As of November 6, 2026, 5 holders' latest Schedule 13D or 13G filings report owning 5% or more of Deep Isolation Nuclear, Inc. The largest reported stake is Elizabeth Muller's, at 22.1%. 6 filings are on record since August 14, 2025 (Schedule 13D, August 18, 2025).
Sell to companies like Deep Isolation Nuclear, Inc? Enter your website and see 10 with a filed reason to buy from you this month. Free.
Opens in a new tab. No signup.
Key facts
- · Holder: Mark N. Tompkins · Percent: 5.5% · SCHEDULE 13G/A
- · Holder: Mark N. Tompkins · Percent: 3.96% · SCHEDULE 13G/A
- · Holder: Elizabeth Muller · Percent: 22.1% · SCHEDULE 13D
- · Holder: Richard Muller · Percent: 5.8% · SCHEDULE 13G
- · Holder: Warren E. Spieker, Jr., individually and as Trustee of the Spieker Living Trust UAD 3/12/02 · Percent: 10.3% · SCHEDULE 13G
Deep Isolation Nuclear, Inc. has 6 Schedule 13D or 13G filings on record since 2025-08-14. 5 holders' latest filing reports 5% or more of common stock, par value $0.0001 per share. Each figure below is the holder's own, as filed, with the filing linked.
Holders
| Holder | Percent | Shares | Latest | Event date |
|---|---|---|---|---|
| 22.1% | 12,663,479 | SCHEDULE 13D, 2025-08-18 | 2025-07-23 | |
| Warren E. Spieker, Jr., individually and as Trustee of the Spieker Living Trust UAD 3/12/02 | 10.3% | 5,903,431 | SCHEDULE 13G, 2025-08-14 | 2025-07-23 |
| 6.5% | 3,745,760 | SCHEDULE 13G, 2025-08-14 | 2025-07-23 | |
| 5.8% | 3,340,560 | SCHEDULE 13G, 2025-08-18 | 2025-07-23 | |
| 5.5% | 3,150,000 | SCHEDULE 13G/A, 2026-05-15 | 2026-03-31 |
Holding shares or following this stake? See who's behind Deep Isolation Nuclear, Inc. and the warning signs.
Free to see. No signup.
Keep reading
More on Deep Isolation Nuclear, Inc. and the records around it.
Companies that share a holder
- Elizabeth Muller also filed stake reports on 1 other company: DEEP FISSION, INC. (Sep 2025)
- Richard Muller also filed stake reports on 1 other company: DEEP FISSION, INC. (Sep 2025)
- Mark N. Tompkins also filed stake reports on 8 other companies: Los Altos Ventures Corp. (Jun 2026), Aeluma, Inc. (May 2026), Deep Fission, Inc. (May 2026)
Watch Deep Isolation Nuclear, Inc.
Get an email when Deep Isolation Nuclear, Inc. files again: a new raise, a leadership change, a layoff or an IPO filing. One email first to confirm; nothing else until you click it. At most one a day, one click to stop. Free for up to 3 companies.
Want the whole picture on Deep Isolation Nuclear, Inc.?
Example from a real report (our sample on Target): “Target eliminated approximately 1,800 corporate positions, with around 1,000 employees receiving layoff notices and the remainder accounted for by eliminating open roles.” Source: NBC News
A Full Report on Deep Isolation Nuclear, Inc.: verified, sourced, every claim cited, ready in a few minutes. See pricing.
What the Full Report on Deep Isolation Nuclear, Inc. covers
The Short Answer
Which Company This Is
What They Do, And How The Money Works
Who Runs It, And How To Reach Them
The Money: Funding, Valuation, Runway
Who Pays Them, And Who They Are Up Against
Warning Bells
Sources
6 cited sources found
Plus the sections for what you are deciding, which you pick after ordering.
A real finished report, first screen. Opens in a new tab.
Not ready to order yet? Keep this snapshot.
Sends this preview to you once; we won't add you to any list
Purpose of Transaction (Item 4)
Elizabeth Muller
The Reporting Person acquired the Common Stock in connection with the Transactions. The information contained in Item 3 of this Schedule 13D is incorporated herein by reference. The Reporting Person serves as a Director and part-time Executive Advisor of the Issuer. Accordingly, the Reporting Person may have influence over the corporate activities of the Issuer, including activities that may relate to items described in clauses (a) through (j) of Item 4 of this Schedule 13D. Subject to the Registration Rights Agreement described in Item 6 of this Schedule 13D, the Reporting Person may, from time to time, purchase or sell securities of the Issuer as appropriate for her personal circumstances. Except as described in this Schedule 13D, the Reporting Person does not have any present plans or proposals that relate to or would result in any of the actions described in clauses (a) through (j) of Item 4 of this Schedule 13D. The Reporting Person reserves the right to formulate plans and/or proposals and to take such actions with respect to her investment in the Issuer, including any or all of the actions set forth in clauses (a) through (j) of Item 4 of this Schedule 13D.Item 4 of the SCHEDULE 13D filed 2025-08-18
Timeline
| Filed | Holder | Percent | Filing |
|---|---|---|---|
| 2025-08-14 | Warren E. Spieker, Jr., individually and as Trustee of the Spieker Living Trust UAD 3/12/02 | 10.3% | SCHEDULE 13G |
| 2025-08-14 | Mercer Robert L. | 6.5% | SCHEDULE 13G |
| 2025-08-18 | Elizabeth Muller | 22.1% | SCHEDULE 13D |
| 2025-08-18 | Richard Muller | 5.8% | SCHEDULE 13G |
| 2025-11-14 | Mark N. Tompkins | 3.96% | SCHEDULE 13G/A |
| 2026-05-15 | Mark N. Tompkins | 5.5% | SCHEDULE 13G/A |
Questions about who owns Deep Isolation Nuclear, Inc.
Who owns Deep Isolation Nuclear, Inc.?
On this page, 5 holders' latest ownership filings report 5% or more of Deep Isolation Nuclear, Inc.: Elizabeth Muller (22.1%, Schedule 13D, filed 2025-08-18), Warren E. Spieker, Jr., individually and as Trustee of the Spieker Living Trust UAD 3/12/02 (10.3%, Schedule 13G, filed 2025-08-14), Mercer Robert L. (6.5%, Schedule 13G, filed 2025-08-14), Richard Muller (5.8%, Schedule 13G, filed 2025-08-18) and Mark N. Tompkins (5.5%, Schedule 13G/A, filed 2026-05-15).
Who are the largest shareholders of Deep Isolation Nuclear, Inc.?
By the share each holder's latest filing reports, the largest holders of Deep Isolation Nuclear, Inc. on this page are Elizabeth Muller (22.1%), Warren E. Spieker, Jr., individually and as Trustee of the Spieker Living Trust UAD 3/12/02 (10.3%) and Mercer Robert L. (6.5%).
When did Elizabeth Muller buy into Deep Isolation Nuclear, Inc.?
The filings give report dates, not purchase dates. The earliest filing from Elizabeth Muller on this page is the Schedule 13D, filed 2025-08-18, reporting 22.1%.
Is this an audit or a full list?
Neither. The ownership list on this page covers only Schedule 13D and 13G filings, which holders make once they own 5% or more of a class of shares (an amendment can report a stake that has since fallen below 5%); 6 such filings are shown here. It is not an audit and not a full cap table: holders who never reached 5% are not listed, and a stake can change after its latest filing.
Tools for this story
Each opens in a new tab, filled in for Deep Isolation Nuclear, Inc.. With no account yet, you sign up free and land on the result.
Where this comes from
Anyone who comes to own more than 5% of a class of a listed company's voting shares has to tell the SEC. A holder who may seek to change or influence the company files Schedule 13D, and has to say in Item 4, "Purpose of Transaction", what it intends to do. A holder with no such intent, such as many index and passive funds, may file the shorter Schedule 13G. Both are amended when the stake changes, including when it falls below 5%.
Every row here is one of those filings, linked to the filing itself. Percentages and share counts are exactly as the holder filed them, for the holder the filing names; an amendment showing a lower figure is shown as filed. Item 4 text is quoted word for word. Where a 13D's Item 4 contains a sentence stating a definite intent to influence the company, that sentence is marked and quoted; the page does not describe the holder or its motives beyond the words it filed. Nothing here is investment advice.