Statement of Changes in Beneficial Ownership (Form 4)

FORM 4 Check this box if no longer subject to Section 16. Form 4 or Form 5 obligations may continue. See Instruction 1(b). Check this box to indicate that a transaction was made pursuant to a contract, instruction or written plan that is intended to satisfy the affirmative defense conditions of Rule 10b5-1(c). See Instruction 10.

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 STATEMENT OF CHANGES IN BENEFICIAL OWNERSHIP OF SECURITIES Filed pursuant to Section 16(a) of the Securities Exchange Act of 1934 or Section 30(h) of the Investment Company Act of 1940

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(Print or Type Responses)

1. Name and Address of Reporting Person * NeoTribe Ventures I, L.P. 2. Issuer Name and Ticker or Trading Symbol BillionToOne, Inc. [BLLN] 5. Relationship of Reporting Person(s) to Issuer (Check all applicable) _____ Director __X__ 10% Owner _____ Officer (give title below) _____ Other (specify below) (Last) (First) (Middle) 1300 EL CAMINO REAL, SUITE 100 3. Date of Earliest Transaction (Month/Day/Year) 11/07/2025 (Street) MENLO PARK, CA 94025 4. If Amendment, Date Original Filed (Month/Day/Year) 6. Individual or Joint/Group Filing (Check Applicable Line) ___ Form filed by One Reporting Person _X_ Form filed by More than One Reporting Person (City) (State) (Zip) Table I - Non-Derivative Securities Acquired, Disposed of, or Beneficially Owned

1.Title of Security (Instr. 3) 2. Transaction Date (Month/Day/Year) 2A. Deemed Execution Date, if any (Month/Day/Year) 3. Transaction Code (Instr. 8) 4. Securities Acquired (A) or Disposed of (D) (Instr. 3, 4 and 5) 5. Amount of Securities Beneficially Owned Following Reported Transaction(s) (Instr. 3 and 4) 6. Ownership Form: Direct (D) or Indirect (I) (Instr. 4) 7. Nature of Indirect Beneficial Ownership (Instr. 4) Code V Amount (A) or (D) Price Common Stock 11/07/2025 C(1) 1,177,800 A (2) 1,297,799 I See Footnote(3) Common Stock 11/07/2025 C(1) 242,216 A (2) 242,216 I See Footnote(4) Common Stock 11/07/2025 C(1) 2,819,490 A (2) 2,819,490 D(5)(6) Common Stock 11/07/2025 J(7) 1,297,799 D (7) 0 I See Footnote(3) Common Stock 11/07/2025 J(7) 242,216 D (7) 0 I See Footnote(4) Common Stock 11/07/2025 J(7) 2,819,490 D (7) 0 D(5)(6) Class A Common Stock 11/07/2025 J(7) 1,297,799 A (7) 1,297,799 I See Footnote(3) Class A Common Stock 11/07/2025 J(7) 242,216 A (7) 242,216 I See Footnote(4) Class A Common Stock 11/07/2025 J(7) 2,819,490 A (7) 2,819,490 D(5)(6)

Reminder: Report on a separate line for each class of securities beneficially owned directly or indirectly.
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Table II - Derivative Securities Acquired, Disposed of, or Beneficially Owned
(e.g., puts, calls, warrants, options, convertible securities)

1. Title of Derivative Security (Instr. 3)	2. Conversion or Exercise Price of Derivative Security	3. Transaction Date (Month/Day/Year)	3A. Deemed Execution Date, if any (Month/Day/Year)	4. Transaction Code (Instr. 8)		5. Number of Derivative Securities Acquired (A) or Disposed of (D) (Instr. 3, 4, and 5)		6. Date Exercisable and Expiration Date (Month/Day/Year)		7. Title and Amount of Underlying Securities (Instr. 3 and 4)		8. Price of Derivative Security (Instr. 5)	9. Number of Derivative Securities Beneficially Owned Following Reported Transaction(s) (Instr. 4)	10. Ownership Form of Derivative Security: Direct (D) or Indirect (I) (Instr. 4)	11. Nature of Indirect Beneficial Ownership (Instr. 4)
				Code	V	(A)	(D)	Date Exercisable	Expiration Date	Title	Amount or Number of Shares
Series B-1 Convertible Preferred Stock	(2)	11/07/2025		C			1,177,800	(2)	(2)	Common Stock	1,177,800	(2)	0	I	See Footnote(3)
Series C Convertible Preferred Stock	(2)	11/07/2025		C			242,216	(2)	(2)	Common Stock	242,216	(2)	0	I	See Footnote(4)
Series A-1 Convertible Preferred Stock	(2)	11/07/2025		C			16,746	(2)	(2)	Common Stock	16,746	(2)	0	D(5)(8)
Series A-3 Convertible Preferred Stock	(2)	11/07/2025		C			19,985	(2)	(2)	Common Stock	19,985	(2)	0	I	See Footnotes(5)(9)
Series A-6 Convertible Preferred Stock	(2)	11/07/2025		C			2,318,482	(2)	(2)	Common Stock	2,318,482	(2)	0	D(5)(10)
Series B-2 Convertible Preferred Stock	(2)	11/07/2025		C			320,363	(2)	(2)	Common Stock	320,363	(2)	0	D(5)(11)
Series C-1 Convertible Preferred Stock	(2)	11/07/2025		C			143,914	(2)	(2)	Common Stock	143,914	(2)	0	D(5)(12)

Reporting Owners

Reporting Owner Name / Address	Relationships
	Director	10% Owner	Officer	Other
NeoTribe Ventures I, L.P. 1300 EL CAMINO REAL, SUITE 100 MENLO PARK, CA 94025		X
Neotribe Ignite Fund I, L.P. 1300 EL CAMINO REAL, SUITE 100 MENLO PARK, CA 94025		X
Neotribe SPV I BTO, LLC 1300 EL CAMINO REAL, SUITE 100 MENLO PARK, CA 94025		X
NeoTribe Associates I, L.P. 1300 EL CAMINO REAL, SUITE 100 MENLO PARK, CA 94025		X
Neotribe Ignite Partners I, LLC 1300 EL CAMINO REAL, SUITE 100 MENLO PARK, CA 94025		X
Neotribe Partners SPV I BTO, LLC 1300 EL CAMINO REAL, SUITE 100 MENLO PARK, CA 94025		X
NeoTribe Partners I, LLC 1300 EL CAMINO REAL, SUITE 100 MENLO PARK, CA 94025		X

Signatures

NeoTribe Ventures I, L.P., by: NeoTribe Partners I, LLC, its general partner, by: /s/ Krishna Kolluri, Managing Member		11/10/2025
**Signature of Reporting Person		Date
NeoTribe Associates I, L.P., by: NeoTribe Partners I, LLC, its general partner, by: /s/ Krishna Kolluri, Managing Member		11/10/2025
**Signature of Reporting Person		Date
Neotribe Ignite Fund I, L.P., by: Neotribe Ignite Partners I, LLC, its general partner, by: /s/ Krishna Kolluri, Managing Member		11/10/2025
**Signature of Reporting Person		Date
Neotribe SPV I BTO, LLC, by: Neotribe Partners SPV I BTO, LLC, its managing member, by: /s/ Krishna Kolluri, Managing Member		11/10/2025
**Signature of Reporting Person		Date
NeoTribe Partners I, LLC, by: /s/ Krishna Kolluri, Managing Member		11/10/2025
**Signature of Reporting Person		Date
Neotribe Ignite Partners I, LLC, by: /s/ Krishna Kolluri, Managing Member		11/10/2025
**Signature of Reporting Person		Date
Neotribe Partners SPV I BTO, LLC, by: /s/ Krishna Kolluri, Managing Member		11/10/2025
**Signature of Reporting Person		Date

Explanation of Responses:

*	If the form is filed by more than one reporting person, see Instruction 4(b)(v).
**	Intentional misstatements or omissions of facts constitute Federal Criminal Violations. See 18 U.S.C. 1001 and 15 U.S.C. 78ff(a).
(1)	The total represents shares received upon conversion of shares of Series A-1 Convertible Preferred Stock, Series A-3 Convertible Preferred Stock, Series A-6 Convertible Preferred Stock, Series B-1 Convertible Preferred Stock, Series B-2 Convertible Preferred Stock, Series C Convertible Preferred Stock and/or Series C-1 Convertible Preferred Stock.
(2)	The reported security converted into the Issuer's Common Stock on a one-for-one basis automatically immediately prior to the closing of the Issuer's initial public offering of Class A common stock (the "Offering") without payment of further consideration. The shares have no expiration date.
(3)	The reported security is directly held by Neotribe Ignite Fund I, L.P. ("NTIF I"). Neotribe Ignite Partners I, LLC ("NTIP I") is the general partner of NTIF I. Krishna Kittu Kolluri ("Kolluri") is the managing member of NTIP I and therefore may be deemed to have voting and dispositive power over the shares held by NTIF I. Kolluri disclaims beneficial ownership of the shares held by NTIF I except to the extent of his pecuniary interest therein.
(4)	The reported security is directly held by Neotribe SPV I BTO, LLC. ("NT SPV I"). Neotribe Partners SPV I BTO, LLC ("NTP SPV I") is the managing member of NT SPV I. Kolluri is the managing member of NTP SPV I and therefore may be deemed to have voting and dispositive power over the shares held by NT SPV I. Kolluri disclaims beneficial ownership of the shares held by NT SPV I except to the extent of his pecuniary interest therein.
(5)	The reported security is directly held by NeoTribe Ventures I, L.P. ("NTV I"), for itself and as nominee for NeoTribe Associates I, L.P. ("NTA I"). NeoTribe Partners I, LLC ("NTP I") is the general partner of NTV I and NTA I. Kolluri is the managing member of NTP I and therefore may be deemed to hold voting and dispositive power over the shares held by NTV I and NTA I. Kolluri disclaims beneficial ownership of the shares held by NTV I and NTA I except to the extent of his pecuniary interest therein.
(6)	Consists of 2,710,286 shares held of record by NTV I for itself and 109,204 shares held of record by NTV I as nominee for NTA I.
(7)	Pursuant to a reclassification exempt under Rule 16b-7, each share of Common Stock was automatically reclassified into one share of Class A common stock immediately prior to the completion of the Offering.
(8)	Consists of 16,098 shares held of record by NTV I for itself and 648 shares held of record by NTV I as nominee for NTA I.
(9)	Consists of 19,211 shares held of record by NTV I for itself and 774 shares held of record by NTV I as nominee for NTA I.
(10)	Consists of 2,228,682 shares held of record by NTV I for itself and 89,800 shares held of record by NTV I as nominee for NTA I.
(11)	Consists of 307,955 shares held of record by NTV I for itself and 12,408 shares held of record by NTV I as nominee for NTA I.
(12)	Consists of 138,340 shares held of record by NTV I for itself and 5,574 shares held of record by NTV I as nominee for NTA I.
Remarks: This Form 4 is one of two Form 4s filed in respect of the conversion and reclassification of the shares held of record by NTIF I, NT SPV I, and NTV I. The Reporting Person for the other Form 4 is Krishna Kittu Kolluri.

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