DEEP FISSION, INC.

Overview

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• TickerFISN on Nasdaq¹
• IndustryElectric Services¹
• HeadquartersBerkeley, California¹
• Incorporated inDE²
• Business address2831 Garber Street, Berkeley, Ca 94705²
• Filer category, Emerging growth company²
• Legal formCorporation

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We are a nuclear energy technology company developing a small modular reactor (“SMR”) based on established pressurized water reactor (“PWR”) technology, with novel emplacement in deep boreholes approximately one mile below the Earth’s surface. Our reactor, which we refer to as the Gravity Reactor, will leverage subsurface conditions to support key containment and operating functions, including the use of hydrostatic pressure from a water column within the borehole to support reactor operating pressure and cooling, and the surrounding geological formation to provide structural confinement and shielding. This approach is intended to reduce reliance on large surface containment structures and other safety-related infrastructure associated with conventional nuclear power plants, support faster deployment timelines, improve security, enhance safety, and enable lower capital and operating cost…³ From its latest annual report

Corporate structure

DEEP FISSION, INC. sits at the top of its group. 1 entity, 1 country on record. Switch between the flow chart and the network, and select any entity to see its details.

Built from major holders from Schedules 13D and 13G. Each entity in the chart links to its source.

What it owns

What DEEP FISSION, INC. reports owning in its annual reports to the SEC: buildings, land and equipment, real estate and locations, investments, intangible assets and inventory, at the end of its latest fiscal year and a year before.

Property and equipment

Investments

Properties, in its own words

We do not currently own any real property. Other than the lease described below, we do not currently lease any facilities. Our corporate, administrative, and engineering functions operate in a decentralized manner, with employees working through a combination of remote and in-person arrangements. Design, development, regulatory, and site-related activities are conducted in person as required by the nature of those functions and applicable regulatory requirements.

In February 2026, in connection with our participation in the DOE Reactor Pilot Program, we entered into a long-term lease for approximately 100 acres located within the Great Plains Industrial Park in Parsons, Kansas. The Kansas Site is being evaluated to support potential future reactor deployment. The lease includes provisions that, upon the satisfaction of specified conditions, require us to purchase the underlying property.

Item 2 of the 10-K filed Apr 15, 2026.³

Leadership

Who has led DEEP FISSION, INC., and when. Pick a name to see everywhere that person has worked.

• Chief executive officerElizabeth Muller Sep 9, 2025 to now¹⁰
• PresidentElizabeth Muller Sep 9, 2025 to now¹⁰
• Chief financial officerWilliam Mark Schmitz Sep 9, 2025 to now¹¹
• Chief operating officerMichael Allen Brasel Mar 10, 2026 to now¹²

Named in SEC Form D filings

People the company listed in its private-offering notices.

• DirectorLeslie S. Goldman Tepper named Feb 18, 2026²²

Former names

• Surfside Acquisition Inc.Mar 21, 2022 to Sep 8, 2025²

Timeline

1. Sep 21, 20268-K Regulation FD disclosure²³
2. Jul 29, 20268-K Other events²⁴
3. Jul 17, 20268-K Executive or director change; Shareholder vote²⁵
4. Jun 22, 20268-K Other events²⁶
5. Apr 22, 20268-K Regulation FD disclosure²⁷
6. Apr 9, 20268-K Earlier financial statements no longer reliable²⁸
7. Mar 5, 20268-K Change of auditor²⁹
8. Feb 25, 20268-K Executive or director change³⁰
9. Feb 10, 20268-K Entered a material agreement; Unregistered sale of shares; Regulation FD disclosure³¹
10. Dec 22, 20258-K Executive or director change; Other events³²
11. Dec 11, 20258-K Executive or director change³³
12. Dec 4, 20258-K Regulation FD disclosure³⁴
13. Sep 9, 2025New chief executive Elizabeth Muller becomes CEO¹⁰

Filings

120 filings to the SEC since October 2021: 4 annual reports, 14 quarterly reports, 18 major events, 44 insider forms, 7 large holders, 3 private raises, 30 other. The latest 20:

1. Sep 21, 20268-K EDGAR
2. Aug 3, 202610-Q EDGAR
3. Jul 29, 20268-K EDGAR
4. Jul 27, 20264 OWNERSHIP DOCUMENT EDGAR
5. Jul 27, 20264 OWNERSHIP DOCUMENT EDGAR
6. Jul 27, 20264 OWNERSHIP DOCUMENT EDGAR
7. Jul 27, 20264 OWNERSHIP DOCUMENT EDGAR
8. Jul 20, 2026S-8 EDGAR
9. Jul 17, 20268-K EDGAR
10. Jun 22, 20268-K EDGAR
11. Jun 18, 2026424B4 EDGAR
12. Jun 17, 2026EFFECT EDGAR
13. Jun 17, 2026CERT EDGAR
14. Jun 17, 2026DEF 14A EDGAR
15. Jun 10, 2026S-1/A EDGAR
16. May 28, 20268-A12B EDGAR
17. May 20, 2026S-1 EDGAR
18. May 15, 2026SCHEDULE 13G/A EDGAR
19. May 8, 202610-Q EDGAR
20. May 1, 2026EFFECT EDGAR

Every filing from the last five years, summarized. The full record is on SEC EDGAR.

Insider trades

2 open-market trades by officers, directors and large owners since October 2021: 1 buys and 1 sales. Grants, option exercises and gifts are left out.

From Forms 4 filed with the SEC.

Major holders

Investors who own more than 5% of the shares must tell the SEC: a 13D if they may seek to influence the company, a 13G if they hold passively.

• Mark N. TompkinsSCHEDULE 13G/A, 3 filings Feb 10, 2023 to May 15, 2026³⁵
• EE Holdings LtdSCHEDULE 13G, 1 filing Nov 3, 2025³⁶
• Elizabeth MullerSCHEDULE 13D, 1 filing Sep 23, 2025³⁷
• Richard MullerSCHEDULE 13D, 1 filing Sep 23, 2025³⁸
• Ian Seth JacobsSC 13G, 1 filing Feb 13, 2023³⁹

Executive pay

What the company paid its top executives, from the summary compensation table in its proxy statement. Total pay includes salary, bonus, stock and option awards and other pay, as the company valued them.

Money raised

Private offerings the company reported to the SEC on Form D.

1. Feb 5, 2026Raised $80 million in a private offering of equity Form D: 223 investors so far Form D
2. Sep 5, 2025Raised $30 million in a private offering of equity Form D: $31.8 million offered in all Form D
3. Sep 5, 2025Filed a private offering of equity Form D: $120 million offered in all Form D

Held by these funds

The largest holders among investment managers' 13F reports for the quarter ending Jun 30, 2026. Change is in shares since the quarter before.

13F reports cover disclosed long positions in U.S. stocks only.

SEC filer profile

How DEEP FISSION, INC. is registered with the Securities and Exchange Commission, from its EDGAR record and the cover page of its latest annual report.

• Name on EDGARDEEP FISSION, INC.¹
• CIK0001918102
• Employer ID (EIN)87-4265302³
• Filer statusNon-accelerated filer an emerging growth company; a smaller reporting company; not a shell company³
• Incorporated inDelaware³
• Fiscal year endsDecember 31¹
• Industry code (SIC)4911 Electric Services¹
• SEC reviewing officeOffice of Energy & Transportation, Division of Corporation Finance¹
• Business address2831 Garber Street, Berkeley, CA 94705¹
• Phone(707) 400-0778¹
• Shares outstanding58,905,938 as of Jul 27, 2026⁸
• Public float$0 as of Dec 31, 2025⁶
• AuditorGRANT THORNTON LLP, Dallas, Texas PCAOB ID 248; no auditor attestation of internal control over financial reporting³
• On EDGAR sinceMar 21, 2022¹
• Filings120 in all: 4 (31), 8-K (18), 10-Q (14), 3 (12), S-1/A (6), 10-K (4), EFFECT (4), 424B3 (3)¹
  All 29 form types

  D (3), S-1 (3), SC 13G (2), SCHEDULE 13D (2), SCHEDULE 13G/A (2), 10-12G (1), 3/A (1), 424B4 (1), 424B5 (1), 8-A12B (1), CERT (1), CORRESP (1), DEF 14A (1), DRS (1), NT 10-K (1), POS AM (1), S-8 (1), SC 14F1 (1), SCHEDULE 13G (1), SEC STAFF ACTION (1), UPLOAD (1)

• Latest filingsAnnual report (10-K) Apr 15, 2026
  Quarterly report (10-Q) Aug 3, 2026
  Proxy statement (DEF 14A) Jun 17, 2026
  Latest 8-K (8-K) Sep 21, 2026

Risk factors and legal proceedings

The risks DEEP FISSION, INC. names in Item 1A of its 10-K filed Apr 15, 2026: 50 risks under these headings, as written.³

• Risks Related to Our Business and Industry
• Our Gravity Reactor is unproven, and our design, borehole development activities, planned pilot reactor, and future commercial applications may fail, progress more slowly than projected, or encounter delays or changes that increase costs and capital requirements.
• We are an early-stage company with a history of operating losses and expect to incur losses for the foreseeable future.
• Our auditor has issued a “going concern” opinion with respect to our financial statements.
• Our business plans require substantial additional capital, and we may not be able to obtain financing on acceptable terms or at all.
• Our technology depends on the successful drilling and long-term stability of deep vertical boreholes, which presents significant technical, engineering, regulatory and operational risks.
• We may be unable to identify, acquire, lease, or otherwise secure access to suitable sites with the geological characteristics necessary to deploy our Gravity Reactor.
• We have no experience operating nuclear power facilities, and our lack of operational experience may create additional risks as we develop and deploy our technology.
• The market for our Gravity Reactor is not yet established and may not achieve the growth potential we expect or may grow more slowly than expected. If demand for our technology fails to develop sufficiently, our business and operations would suffer, and we would be unable to achieve or maintain profitability.
• Our ability to deploy reactors commercially will depend on our ability to enter into long-term power purchase agreements or other commercial arrangements with customers.
• Our future revenue plans depend in part on strategic partners and government entities.
• Electricity generated by our Gravity Reactors may not be cost-competitive with other energy generation technologies, and competing energy solutions could reduce demand for our reactors and related services.

Legal proceedings

From time to time, we may become involved in litigation, investigations, claims or legal proceedings arising in the ordinary course of business. Litigation, investigations, claims and other legal proceedings are subject to inherent uncertainties, and an adverse outcome in one or more matters could occur and may have a material adverse effect on our business, prospects, results of operations, and financial condition. Except as described below, we are not aware of any material pending legal proceedings to which we are a party.

In April 2025, we joined as a plaintiff, together with the State of Texas, State of Utah, State of Louisiana, State of Florida, the Arizona State Legislature (by and through the President of the Arizona Senate and the Speaker of the Arizona House of Representatives), Last Energy, Inc., and Valar Atomics Inc., in a federal lawsuit filed in the U.S. District Court for the Eastern District of Texas against the NRC, captioned State of Texas et al. v. U.S. Nuclear Regulatory Commission (Case No. 6:24-cv-00507).The lawsuit challenges the NRC’s interpretation and application of certain licensing regulations under the AEA, including the NRC’s longstanding definition of “utilization facility.” The complaint seeks declaratory and injunctive relief requiring the NRC to revise its licensing framework and undertake new rulemaking under the APA.

The case remains in its early stages, and no substantive rulings have been issued. We cannot predict the outcome of this proceeding or the potential impact it may have on federal or state regulatory processes applicable to advanced reactor technologies or on the timing or evaluation of any applications we may submit to the NRC. See Item 1A, “Risk Factors” of this Annual Report.

The opening of Item 3, Legal Proceedings.³