X0508 4 2025-11-06 0002070849 BillionToOne, Inc. BLLN 0002087538 Bremner Thomas S 1 NORTH WACKER DRIVE, SUITE 2200 CHICAGO IL 60606-2807 true false false false false Common Stock 2025-11-06 4 A false 8333 0 A 8333 D Common Stock 2025-11-07 4 C false 152440 A 152440 I See Footnotes Common Stock 2025-11-07 4 C false 155711 A 155711 I See Footnotes Common Stock 2025-11-07 4 C false 176271 A 176271 I See Footnotes Common Stock 2025-11-07 4 C false 269918 A 269918 I See Footnotes Common Stock 2025-11-07 4 C false 240072 A 240072 I See Footnotes Common Stock 2025-11-07 4 C false 675352 A 675352 I See Footnotes Common Stock 2025-11-07 4 C false 277508 A 277508 I See Footnotes Common Stock 2025-11-07 4 J false 8333 D 0 D Common Stock 2025-11-07 4 J false 152440 D 0 I See Footnotes Common Stock 2025-11-07 4 J false 155711 D 0 I See Footnotes Common Stock 2025-11-07 4 J false 176271 D 0 I See Footnotes Common Stock 2025-11-07 4 J false 269918 D 0 I See Footnotes Common Stock 2025-11-07 4 J false 240072 D 0 I See Footnotes Common Stock 2025-11-07 4 J false 675352 D 0 I See Footnotes Common Stock 2025-11-07 4 J false 277508 D 0 I See Footnotes Class A Common Stock 2025-11-07 4 J false 8333 A 8333 D Class A Common Stock 2025-11-07 4 J false 152440 A 152440 I See Footnotes Class A Common Stock 2025-11-07 4 J false 155711 A 155711 I See Footnotes Class A Common Stock 2025-11-07 4 J false 176271 A 176271 I See Footnotes Class A Common Stock 2025-11-07 4 J false 269918 A 269918 I See Footnotes Class A Common Stock 2025-11-07 4 J false 240072 A 240072 I See Footnotes Class A Common Stock 2025-11-07 4 J false 675352 A 675352 I See Footnotes Class A Common Stock 2025-11-07 4 J false 277508 A 277508 I See Footnotes Class A Common Stock 2025-11-07 4 P false 4016 60 A 156456 I See Footnotes Class A Common Stock 2025-11-07 4 P false 4084 60 A 159795 I See Footnotes Class A Common Stock 2025-11-07 4 P false 3462 60 A 179733 I See Footnotes Class A Common Stock 2025-11-07 4 P false 5446 60 A 275364 I See Footnotes Class A Common Stock 2025-11-07 4 P false 6867 60 A 246939 I See Footnotes Class A Common Stock 2025-11-07 4 P false 17791 60 A 693143 I See Footnotes Series A-1 Convertible Preferred Stock 2025-11-07 4 C false 1352 D Common Stock 1352 0 I See Footnotes Series C Convertible Preferred Stock 2025-11-07 4 C false 114117 D Common Stock 114117 0 I See Footnotes Series C-1 Convertible Preferred Stock 2025-11-07 4 C false 16747 D Common Stock 16747 0 I See Footnotes Series D Convertible Preferred Stock 2025-11-07 4 C false 20224 D Common Stock 20224 0 I See Footnotes Series C Convertible Preferred Stock 2025-11-07 4 C false 121688 D Common Stock 121688 0 I See Footnotes Series C-1 Convertible Preferred Stock 2025-11-07 4 C false 17858 D Common Stock 17858 0 I See Footnotes Series D Convertible Preferred Stock 2025-11-07 4 C false 16165 D Common Stock 16165 0 I See Footnotes Series A-1 Convertible Preferred Stock 2025-11-07 4 C false 1562 D Common Stock 1562 0 I See Footnotes Series C Convertible Preferred Stock 2025-11-07 4 C false 131888 D Common Stock 131888 0 I See Footnotes Series C-1 Convertible Preferred Stock 2025-11-07 4 C false 19355 D Common Stock 19355 0 I See Footnotes Series D Convertible Preferred Stock 2025-11-07 4 C false 23466 D Common Stock 23466 0 I See Footnotes Series A-1 Convertible Preferred Stock 2025-11-07 4 C false 1864 D Common Stock 1864 0 I See Footnotes Series C Convertible Preferred Stock 2025-11-07 4 C false 157404 D Common Stock 157404 0 I See Footnotes Series C-1 Convertible Preferred Stock 2025-11-07 4 C false 23100 D Common Stock 23100 0 I See Footnotes Series D Convertible Preferred Stock 2025-11-07 4 C false 87550 D Common Stock 87550 0 I See Footnotes Series A-1 Convertible Preferred Stock 2025-11-07 4 C false 652 D Common Stock 652 0 I See Footnotes Series C Convertible Preferred Stock 2025-11-07 4 C false 55091 D Common Stock 55091 0 I See Footnotes Series C-1 Convertible Preferred Stock 2025-11-07 4 C false 8084 D Common Stock 8084 0 I See Footnotes Series D Convertible Preferred Stock 2025-11-07 4 C false 176245 D Common Stock 176245 0 I See Footnotes Series A-1 Convertible Preferred Stock 2025-11-07 4 C false 5988 D Common Stock 5988 0 I See Footnotes Series C Convertible Preferred Stock 2025-11-07 4 C false 505570 D Common Stock 505570 0 I See Footnotes Series C-1 Convertible Preferred Stock 2025-11-07 4 C false 74195 D Common Stock 74195 0 I See Footnotes Series D Convertible Preferred Stock 2025-11-07 4 C false 89599 D Common Stock 89599 0 I See Footnotes Series A-1 Convertible Preferred Stock 2025-11-07 4 C false 1078 D Common Stock 1078 0 I See Footnotes Series C Convertible Preferred Stock 2025-11-07 4 C false 91003 D Common Stock 91003 0 I See Footnotes Series C-1 Convertible Preferred Stock 2025-11-07 4 C false 13355 D Common Stock 13355 0 I See Footnotes Series D Convertible Preferred Stock 2025-11-07 4 C false 122072 D Common Stock 122072 0 I See Footnotes Each restricted stock unit ("RSU") represents a contingent right to receive one share of the Issuer's Common Stock. The RSUs shall vest over three years in equal annual installments on the anniversary of November 6, 2025, subject to the Reporting Person's continuous service to the Issuer through each such vesting date. The total represents shares received upon conversion of shares of Series A-1 Convertible Preferred Stock, Series C Convertible Preferred Stock, Series C-1 Convertible Preferred Stock and/or Series D Convertible Preferred Stock. 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. The reported security is directly held by Adams Street 2019 Direct Growth Equity Fund LP. The reported security is directly held by Adams Street 2020 Direct Growth Equity Fund LP. The reported security is directly held by Adams Street 2021 Direct Growth Equity Fund LP. The reported security is directly held by Adams Street 2022 Direct Growth Equity Fund LP. The reported security is directly held by Adams Street Private Equity Navigator Fund LLC (f/k/a Adams Street Global Private Markets Fund LP). The reported security is directly held by Adams Street Growth Equity Fund VII LP. The reported security is directly held by FCPR GF - Lumyna Private Equity World Fund. Adams Street Partners, LLC is the managing member of the general partner of each of Adams Street 2019 Direct Growth Equity Fund LP, Adams Street 2020 Direct Growth Equity Fund LP, Adams Street 2021 Direct Growth Equity Fund LP, Adams Street 2022 Direct Growth Equity Fund LP, Adams Street Growth Equity Fund VII LP, and Adams Street Private Equity Navigator Fund LLC (f/k/a Adams Street Global Private Markets Fund LP) (collectively, the U.S. Funds) and, as a result, may be deemed to beneficially own the shares held by the U.S. Funds. Furthermore, Adams Street Partners, LLC, is the Sous-Delegataire Financier of the Delegataire Financier of the management company of FCPR GF - Lumyna Private Equity World Fund (Lumyna and together with the U.S. Funds, the Funds) and, as a result, may be deemed to beneficially own the shares held by Lumyna. (Continued from footnote 11) Thomas S. Bremner, Jeffrey T. Diehl, Brian Dudley, Elisha P. Gould, Robin Murray and Fred Wang, each of whom is a partner of Adams Street Partners, LLC (or a subsidiary thereof), may be deemed to have shared voting, investment and dispositive power over the shares held by the Funds. The Reporting Person disclaims beneficial ownership of these shares except to the extent of his pecuniary interest therein. 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. /s/ Thomas P. Lynch, Attorney-in-Fact 2025-11-10