Table of Contents As filed with the Securities and Exchange Commission on October 7, 2025. Registration Statement No. 333- UNITED STATES SECURITIES AND EXCHANGE COMMISSION WASHINGTON, D.C. 20549 FORM S-1 REGISTRATION STATEMENT UNDER THE SECURITIES ACT OF 1933 BILLIONTOONE, INC. (Exact name of Registrant as specified in its charter) (State or other jurisdiction of incorporation or organization) Delaware 8071 81-1082020 (Primary Standard Industrial Classification Code Number) 1035 O'Brien Drive Menlo Park, CA ...