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            4</title><style type="text/css">
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      </style></head><body>SEC Form 4 
   <table width="100%" border="0" cellspacing="0" cellpadding="4"><tr><td width="20%" colspan="2" valign="top" align="center" class="FormName">FORM 4</td><td rowspan="2" width="60%" valign="middle" align="center"><span class="FormTitle">UNITED STATES SECURITIES AND EXCHANGE COMMISSION</span><br><span class="MedSmallFormText">Washington, D.C. 20549</span><br><br><span class="FormTitle">STATEMENT OF CHANGES IN BENEFICIAL OWNERSHIP</span><br><br><span class="MedSmallFormText">Filed pursuant to Section 16(a) of the Securities Exchange Act of 1934</span><br><span class="MedSmallFormText">or Section 30(h) of the Investment Company Act of 1940</span></td><td rowspan="2" width="20%" valign="top" align="center"><table width="100%" border="1" summary="OMB Approval Status Box"><tr><td class="FormTextC">OMB APPROVAL</td></tr><tr><td><table width="100%" border="0" summary="OMB Interior Box"><tr><td class="SmallFormText" colspan="3">OMB Number:</td><td class="SmallFormTextR">3235-0287</td></tr><tr><td class="SmallFormText" colspan="4">Estimated average burden</td></tr><tr><td class="SmallFormText" colspan="3">hours per response:</td><td class="SmallFormTextR">0.5</td></tr></table></td></tr></table></td></tr><tr valign="middle"><td><table width="100%" border="1" cellpadding="0" cellspacing="0"><tr><td>  </td></tr></table></td><td class="SmallFormText">Check this box if no longer subject to Section 16. Form 4 or Form 5 obligations may continue. 
         <i>See</i>

         Instruction 1(b).</td></tr><tr valign="middle"><td><table width="100%" border="1" cellpadding="0" cellspacing="0"><tr><td>  </td></tr></table></td><td class="SmallFormText">Check this box to indicate that a transaction was made pursuant to a contract, instruction or written plan for the purchase or sale of equity securities of the issuer that is intended to satisfy the affirmative defense conditions of Rule 10b5-1(c). See Instruction 10. </td></tr></table><table width="100%" border="1" cellspacing="0" cellpadding="4"><tr><td rowspan="4" width="35%" valign="top"><span class="MedSmallFormText">1. Name and Address of Reporting Person<sup>*</sup></span><table border="0" width="100%"><tr><td><a href="/cgi-bin/browse-edgar?action=getcompany&amp;CIK=0001534264">Casdin Eli</a></td></tr></table><hr width="98%"><table border="0" width="100%"><tr><td width="33%" class="MedSmallFormText">(Last)</td><td width="33%" class="MedSmallFormText">(First)</td><td width="33%" class="MedSmallFormText">(Middle)</td></tr></table><table border="0" width="100%"><tr><td><span class="FormData">C/O STANDARD BIOTOOLS INC.</span></td></tr><tr><td><span class="FormData">50 MILK STREET, 10TH FLOOR</span></td></tr></table><hr width="98%"><span class="MedSmallFormText">(Street)</span><table border="0" width="100%"><tr><td width="33%"><span class="FormData">BOSTON</span></td><td width="33%"><span class="FormData">
				MASSACHUSETTS
			</span></td><td width="33%"><span class="FormData">02109</span></td></tr></table><hr width="98%"><table border="0" width="100%"><tr><td width="33%" class="MedSmallFormText">(City)</td><td width="33%" class="MedSmallFormText">(State)</td><td width="33%" class="MedSmallFormText">(Zip)</td></tr></table><hr width="98%"><table border="0" width="100%"><tr><td width="33%" colspen="3"><span class="FormData">UNITED STATES</span></td></tr></table><hr width="98%"><span class="MedSmallFormText">(Country)</span></td><td width="35%" valign="top"><span class="MedSmallFormText">2. Issuer Name <b>and</b> Ticker or Trading Symbol
      </span><br><a href="/cgi-bin/browse-edgar?action=getcompany&amp;CIK=0001162194">STANDARD BIOTOOLS INC.</a>
     [ <span class="FormData">LAB</span> ]
   </td><td rowspan="2" valign="top"><span class="MedSmallFormText">5. Relationship of Reporting Person(s) to Issuer
      </span><br><span class="MedSmallFormText">(Check all applicable)</span><table border="0" width="100%"><tr><td width="15%" align="center"><span class="FormData">X</span></td><td width="35%" class="MedSmallFormText">Director</td><td width="15%" align="center"><span class="FormData">X</span></td><td width="35%" class="MedSmallFormText">10% Owner</td></tr><tr><td align="center"></td><td class="MedSmallFormText">Officer (give title below)</td><td align="center"></td><td class="MedSmallFormText">Other (specify below)</td></tr><tr><td width="15%" align="center"></td><td width="35%" align="left" style="color: blue"></td><td width="15%" align="center"></td><td width="35%" align="left" style="color: blue"></td></tr></table></td></tr><tr><td valign="top"><span class="MedSmallFormText">2a. Foreign Trading Symbol
		 <br></span></td></tr><tr><td valign="top"><span class="MedSmallFormText">3. Date of Earliest Transaction
         (Month/Day/Year)</span><br><span class="FormData">06/18/2026</span></td><td valign="top" rowspan="2"><span class="MedSmallFormText">6. Individual or Joint/Group Filing (Check Applicable Line)
      </span><table border="0" width="100%"><tr><td width="15%" align="center"><span class="FormData">X</span></td><td width="85%" class="MedSmallFormText">Form filed by One Reporting Person</td></tr><tr><td width="15%" align="center"></td><td width="85%" class="MedSmallFormText">Form filed by More than One Reporting Person</td></tr></table></td></tr><tr><td valign="top" rowspan="1"><span class="MedSmallFormText">4. If Amendment, Date of Original Filed
         (Month/Day/Year)</span><br><br></td></tr></table><table width="100%" border="1" cellspacing="0" cellpadding="4"><thead><tr><th width="100%" valign="top" colspan="11" align="center" class="FormTextC"><b>Table I - Non-Derivative Securities Acquired, Disposed of, or Beneficially Owned</b></th></tr><tr><th width="36%" valign="top" rowspan="2" align="left" class="MedSmallFormText">1. Title of Security (Instr. 
      3)
   </th><th width="6%" valign="top" rowspan="2" align="left" class="SmallFormText">2. Transaction Date
      (Month/Day/Year)</th><th width="5%" valign="top" rowspan="2" align="left" class="SmallFormText">2A. Deemed Execution Date, if any
      (Month/Day/Year)</th><th width="7%" valign="top" colspan="2" align="left" class="SmallFormText">3. Transaction Code (Instr. 
      8)
   </th><th width="19%" valign="top" colspan="3" align="left" class="SmallFormText">4. Securities Acquired (A) or Disposed Of (D) (Instr. 
      3, 4 and 5)
   </th><th width="11%" valign="top" rowspan="2" align="left" class="SmallFormText">5. 
      Amount of Securities Beneficially Owned Following Reported Transaction(s) (Instr. 
      3 and 4)
   </th><th width="9%" valign="top" rowspan="2" align="left" class="SmallFormText">6. Ownership Form: Direct (D) or Indirect (I) (Instr. 
      4)
   </th><th width="8%" valign="top" rowspan="2" align="left" class="SmallFormText">7. Nature of Indirect Beneficial Ownership (Instr. 
      4)
   </th></tr><tr><th width="4%" align="center" class="SmallFormText">Code</th><th width="3%" align="center" class="SmallFormText">V</th><th width="8%" align="center" class="SmallFormText">Amount</th><th width="5%" align="center" class="SmallFormText">(A) or (D)</th><th width="6%" align="center" class="SmallFormText">Price</th></tr></thead><tbody><tr><td align="left"><span class="FormData">Common Stock</span></td><td align="center"><span class="FormData">06/18/2026</span></td><td align="center"></td><td align="center"><span class="SmallFormData">A</span></td><td align="center"></td><td align="center"><span class="FormData">99,116</span><span class="FootnoteData"><sup>(1)</sup></span></td><td align="center"><span class="FormData">A</span></td><td align="center"><span class="FormText">$</span><span class="FormData">0</span></td><td align="center"><span class="FormData">3,053,169</span></td><td align="center"><span class="FormData">D</span></td><td align="left"></td></tr><tr><td align="left"><span class="FormData">Common Stock</span></td><td align="center"></td><td align="center"></td><td align="center"></td><td align="center"></td><td align="center"></td><td align="center"></td><td align="center"></td><td align="center"><span class="FormData">13,939,637</span></td><td align="center"><span class="FormData">I</span></td><td align="left"><span class="FormData">Casdin Private Growth Equity Fund II, L.P.</span><span class="FootnoteData"><sup>(2)</sup></span></td></tr><tr><td align="left"><span class="FormData">Common Stock</span></td><td align="center"></td><td align="center"></td><td align="center"></td><td align="center"></td><td align="center"></td><td align="center"></td><td align="center"></td><td align="center"><span class="FormData">2,744,219</span></td><td align="center"><span class="FormData">I</span></td><td align="left"><span class="FormData">By Casdin Private Growth Equity Fund, L.P.</span><span class="FootnoteData"><sup>(3)</sup></span></td></tr><tr><td align="left"><span class="FormData">Common Stock</span></td><td align="center"></td><td align="center"></td><td align="center"></td><td align="center"></td><td align="center"></td><td align="center"></td><td align="center"></td><td align="center"><span class="FormData">72,100,000</span></td><td align="center"><span class="FormData">I</span></td><td align="left"><span class="FormData">Casdin Partners Master Fund, L.P.</span><span class="FootnoteData"><sup>(4)</sup></span></td></tr></tbody></table><table width="100%" border="1" cellspacing="0" cellpadding="4"><thead><tr><th width="100%" valign="top" colspan="16" align="center" class="FormTextC"><b>Table II - Derivative Securities Acquired, Disposed of, or Beneficially Owned</b><br><b>(e.g., puts, calls, warrants, options, convertible securities)</b></th></tr><tr><th width="13%" valign="top" rowspan="2" align="left" class="SmallFormText">1. Title of Derivative Security (Instr. 
      3)
   </th><th width="5%" valign="top" rowspan="2" align="left" class="SmallFormText">2. Conversion or Exercise Price of Derivative Security
   </th><th width="5%" valign="top" rowspan="2" align="left" class="SmallFormText">3. Transaction Date
      (Month/Day/Year)</th><th width="5%" valign="top" rowspan="2" align="left" class="SmallFormText">3A. Deemed Execution Date, if any
      (Month/Day/Year)</th><th width="9%" valign="top" colspan="2" align="left" class="SmallFormText">4. Transaction Code (Instr. 
      8)
   </th><th width="10%" valign="top" colspan="2" align="left" class="SmallFormText">5. 
      Number of Derivative Securities Acquired (A) or Disposed of (D) (Instr. 
      3, 4 and 5)
   </th><th width="9%" valign="top" colspan="2" align="left" class="SmallFormText">6. Date Exercisable and Expiration Date 
      (Month/Day/Year)</th><th width="17%" valign="top" colspan="2" align="left" class="SmallFormText">7. Title and Amount of Securities Underlying Derivative Security (Instr. 
      3 and 4)
   </th><th width="6%" valign="top" rowspan="2" align="left" class="SmallFormText">8. Price of Derivative Security (Instr. 
      5)
   </th><th width="6%" valign="top" rowspan="2" align="left" class="SmallFormText">9. 
      Number of derivative Securities Beneficially Owned Following Reported Transaction(s) (Instr. 
      4)
   </th><th width="6%" valign="top" rowspan="2" align="left" class="SmallFormText">10. Ownership Form: Direct (D) or Indirect (I) (Instr. 
      4)
   </th><th width="7%" valign="top" rowspan="2" align="left" class="SmallFormText">11. Nature of Indirect Beneficial Ownership (Instr. 
      4)
   </th></tr><tr><th width="4%" valign="bottom" align="center" class="SmallFormText">Code</th><th width="4%" valign="bottom" align="center" class="SmallFormText">V</th><th width="5%" valign="bottom" align="center" class="SmallFormText">(A)</th><th width="5%" valign="bottom" align="center" class="SmallFormText">(D)</th><th width="5%" valign="bottom" align="center" class="SmallFormText">Date Exercisable</th><th width="4%" valign="bottom" align="center" class="SmallFormText">Expiration Date</th><th width="10%" valign="bottom" align="center" class="SmallFormText">Title</th><th width="7%" valign="bottom" align="center" class="SmallFormText">Amount or Number of Shares</th></tr></thead><tbody><tr><td align="left"><span class="SmallFormData">Stock Option (Right to buy)</span></td><td align="center"><span class="SmallFormText">$</span><span class="SmallFormData">0.8297</span></td><td align="center"><span class="SmallFormData">06/18/2026</span></td><td align="center"></td><td align="center"><span class="SmallFormData">A</span></td><td align="center"></td><td align="center"><span class="SmallFormData">175,923</span></td><td align="center"></td><td align="center"><span class="SmallFormData">
                
            </span><span class="FootnoteData"><sup>(5)</sup></span></td><td align="center"><span class="SmallFormData">06/18/2036</span></td><td align="center"><span class="SmallFormData">Common Stock</span></td><td align="center"><span class="FormData">175,923</span></td><td align="center"><span class="SmallFormText">$</span><span class="SmallFormData">0</span></td><td align="center"><span class="SmallFormData">175,923</span></td><td align="center"><span class="SmallFormData">D</span></td><td align="left"></td></tr></tbody></table><table border="0" width="100%"><tr><td class="MedSmallFormText"><b>Explanation of Responses:</b></td></tr><tr><td class="FootnoteData">1. Represents Restricted Stock Units ("RSUs") that vest in full on the earlier to occur of June 18, 2027 and one day prior to the date of the Company's next annual meeting of stockholders, subject to the Reporting Person's continued service through the applicable vesting date. Each RSU represents the right to receive one share of common stock upon vesting.</td></tr><tr><td class="FootnoteData">2. The securities are owned directly by Casdin Private Growth Equity Fund II, L.P. (the "Equity Fund II") and may be deemed to be indirectly beneficially owned by (i) Casdin Capital, LLC ("Casdin"), the investment adviser to the Equity Fund II, and (ii) Eli Casdin, the managing member of Casdin.</td></tr><tr><td class="FootnoteData">3. The securities are owned directly by Casdin Private Growth Equity Fund, L.P. (the "Equity Fund") and may be deemed to be indirectly beneficially owned by (i) Casdin, the investment adviser to the Equity Fund, and (ii) Eli Casdin, the managing member of Casdin.</td></tr><tr><td class="FootnoteData">4. The securities are owned directly by Casdin Partners Master Fund, L.P. (the "Master Fund") and may be deemed to be indirectly beneficially owned by (i) Casdin, the investment adviser to the Master Fund, (ii) Casdin Partners GP, LLC, the general partner of the Master Fund (the "GP"), and (iii) Eli Casdin, the managing member of Casdin and the GP.</td></tr><tr><td class="FootnoteData">5. The Option becomes exercisable in twelve equal monthly installments beginning on July 18, 2026, subject to the Reporting Person's continued service through the applicable vesting date.</td></tr><tr><td class="FormText"><b>Remarks:</b></td></tr><tr><td class="FootnoteData">The Reporting Person disclaims beneficial ownership in the securities reported on this Form 4 except to the extent of his pecuniary interest, if any, therein, and this report shall not be deemed to be an admission that the Reporting Person is the beneficial owner of such securities for purposes of Section 16 or for any other purpose.</td></tr></table><table width="100%" border="0"><tr><td width="60%"></td><td width="20%"><u><span class="FormData">/s/ Eli Casdin</span></u></td><td width="20%"><u><span class="FormData">06/23/2026</span></u></td></tr><tr><td></td><td class="MedSmallFormText">** Signature of Reporting Person</td><td class="MedSmallFormText">Date</td></tr><tr><td colspan="3" class="MedSmallFormText">Reminder: Report on a separate line for each class of securities beneficially owned directly or indirectly.</td></tr><tr><td colspan="3" class="MedSmallFormText">* If the form is filed by more than one reporting person, 
                  <i>see</i>

                  Instruction 
                  4

                  (b)(v).</td></tr><tr><td colspan="3" class="MedSmallFormText">** Intentional misstatements or omissions of facts constitute Federal Criminal Violations 
                  <i>See</i>

                  18 U.S.C. 1001 and 15 U.S.C. 78ff(a).</td></tr><tr><td colspan="3" class="MedSmallFormText">Note: File three copies of this Form, one of which must be manually signed. If space is insufficient, 
                  <i>see</i>

                  Instruction 6 for procedure.</td></tr><tr><td colspan="3" class="MedSmallFormText"><b>Persons who respond to the collection of information contained in this form are not required to respond unless the form displays a currently valid OMB Number.</b></td></tr><tr><td colspan="3" class="MedSmallFormText"><b>* Form 4: SEC 1474 (03-26)</b></td></tr></table></body></html>
