Comparable stake leader
Elizabeth Muller
SEC ownership of DEEP FISSION, INC.
Top holders, 13D/G large-stake signals, insider positions, and transaction flow tied to CIK 0001918102.
Disclosed value leader
—
Comparable rows
4/13
Latest evidence
28 Apr 2026
- Public ticker
- FISN
- Parsed ownership sources
-
3/4/5 and 13D/G
Source: Parsed SEC ownership filingsUse: Compare filing families carefully
- Largest SEC-reported holder
-
Elizabeth Muller
Ranking: Comparable ownership first, then disclosed value
- Comparable ownership rows
-
4 of 13
Meaning: Rows with safely comparable ownership %
- Latest 13D/G holder
-
Elizabeth Muller
Source: Latest parsed Schedule 13D/G stake
- Latest parsed ownership date
-
28 Apr 2026
Freshness: Most recent filing date in this holder set
- Issuer CIK
- 0001918102
- Issuer location
- Berkeley, CA
Ownership snapshot
CIK-linked ownership evidence from parsed SEC filings.
3 signals
Issuer
Names, identifiers, and filing context for this profile.
2 identity fields
Ownership snapshot
Top shareholders of DEEP FISSION, INC. (13F + 13D/G + 3/4/5)
Grouped by holder across the latest SEC ownership disclosures. Start with comparable ownership when available, then verify the linked 13F, 13D/G, or 3/4/5 evidence.
Comparable stake leader
Elizabeth Muller
Disclosed value leader
—
Comparable rows
4/13
Latest evidence
28 Apr 2026
3/4/5
13D/G
Lead comparable stake: 21%
9 rows are not safely comparable across share classes.
13D/G row: Elizabeth Muller
Showing 1-8 of 13 holder rows.
Quick read
Elizabeth Muller leads the comparable SEC ownership view at 21%.
4 of 13 rows have a safely comparable ownership percentage. Use this as a filing-backed starting point, then open the detailed table for source links, reporting role, position value, share count, and filing date.
Open SEC evidence
Opens Elizabeth Muller's linked filing trail.
Comparable ownership
Top 4
Elizabeth Muller
21%
Richard Muller
11%
Mark N. Tompkins
5.6%
EE Holdings Ltd
5.5%
Ownership % is shown only when SEC disclosures are safely comparable across share classes.
Detailed SEC evidence table Showing 1-8 of 13 holder rows
| Holder | Evidence | Ownership % | Position | 12M Net Δ | As of |
|---|---|---|---|---|---|
| Elizabeth Muller |
3/4/5
13D/G
Chief Executive Officer · Muller Elizabeth
|
21%
from 13D/G
|
—
15,948,881 shares
mixed-class rows
|
— | 09 Mar 2026 |
| Richard Muller |
3/4/5
13D/G
Chief Technology Officer · Muller Richard
|
11%
from 13D/G
|
—
6,068,789 shares
mixed-class rows
|
— | 09 Mar 2026 |
| Mark N. Tompkins |
13D/G
3/4/5
The reporting person is a former director and former 10% owner in the Issuer.
|
5.6%
|
—
3,158,333 shares
|
$0 | 31 Mar 2026 |
| EE Holdings Ltd |
13D/G
EE HOLDINGS LIMITED
|
5.5%
|
—
2,866,667 shares
|
$0 | 30 Sep 2025 |
| Michael Allen Brasel |
3/4/5
Chief Operating Officer
|
—
class O/S missing
|
—
530,000 shares
|
— | 09 Mar 2026 |
| Jonathon Angell |
3/4/5
Director
|
—
mixed-class rows
|
—
427,851 shares
mixed-class rows
|
— | 09 Mar 2026 |
| Mark Wayne Peres |
3/4/5
Chief Nuclear Officer
|
—
mixed-class rows
|
—
374,607 shares
mixed-class rows
|
— | 09 Mar 2026 |
| Leslie Goldman Tepper |
3/4/5
Director
|
—
mixed-class rows
|
—
337,330 shares
mixed-class rows
|
— | 28 Apr 2026 |
How to read this table
Rows are grouped by holder and ranked first by SEC-reported ownership % when it is safely comparable, then by disclosed holdings value. — indicates unavailable or non-comparable values; "mixed-class rows" means the latest filing spans non-comparable classes.
Forms 3/4/5 flow
Insider trading overview
Insider buy and sell flow is broadly balanced over the last 12 months. No Buy or Sell transactions have been reported since 07 Jul 2025.
Buys
$0
Insiders: 0
Sells
$0
Insiders: 0
Net
$0
Shares: 0
Window
Last 12 months
4 rolling buckets
Buy value
Sell value
Shares: 0
Shares: 0
| Window (months) | Buy shares | Sell shares | Buy value | Sell value | Net value |
|---|---|---|---|---|---|
| 0-3 | 0 | 0 | $0 | $0 | $0 |
| 3-6 | 0 | 0 | $0 | $0 | $0 |
| 6-9 | 0 | 0 | $0 | $0 | $0 |
| 9-12 | 0 | 0 | $0 | $0 | $0 |
Reporting owners
Insider holders from Forms 3/4/5
Showing 1-12 of 12 reporting-owner rows connected to DEEP FISSION, INC.. Open a relationship link for the CIK-to-CIK filing trail.
Rows
12
Largest Forms 3/4/5 holder
Michael Allen Brasel
Net 12M change
$0
Latest report
28 Apr 2026
| Name | Relationship | Holdings Value | Past Year Net Change | Change % | Valuation | Report Date |
|---|---|---|---|---|---|---|
| Michael Allen Brasel | Chief Operating Officer | Mixed | 09 Mar 2026 | |||
| Elizabeth Muller | Chief Executive Officer | Mixed | 09 Mar 2026 | |||
| Leslie Goldman Tepper | Director | Mixed | 28 Apr 2026 | |||
| Jonathon Angell | Director | Mixed | 09 Mar 2026 | |||
| Thomas S. Glanville | Director | Mixed | 09 Mar 2026 | |||
| Blake Janover | Director | Mixed | 09 Mar 2026 | |||
| Richard Muller | Chief Technology Officer | Mixed | 09 Mar 2026 | |||
| Mark Wayne Peres | Chief Nuclear Officer | Mixed | 09 Mar 2026 | |||
| Jonathan H. Gordon | General Counsel | Mixed | 09 Mar 2026 | |||
| William A. Schmitz | Chief Financial Officer | Mixed | 09 Mar 2026 | |||
| Mark N. Tompkins | The reporting person is a former director and former 10% owner in the Issuer. | Mixed | 05 Sep 2025 | |||
| Ian Seth Jacobs | President, CEO, CFO, Secretary, Director | Mixed | 26 Aug 2025 |
Recent insider transactions for DEEP FISSION, INC.
Showing up to 300 recent insider transactions from the last 12 months.
| Insider | Symbol | Class | Transaction | % | SEC-reported value | SEC-reported price | Shares | Shares owned | Date | Ownership |
|---|---|---|---|---|---|---|---|---|---|---|
| Blake Janover | Restricted Stock Unit | Award | 3.33% | 3,334 | 103,334 | 09 Mar 2026 | Direct | |||
| Elizabeth Muller | Employee Stock Option (right to buy) | Award | 167.7% | 2,600,000 | 4,150,300 | 09 Mar 2026 | Direct | |||
| Richard Muller | Employee Stock Option (right to buy) | Award | 34.3% | 223,000 | 872,363 | 09 Mar 2026 | Direct | |||
| Michael Allen Brasel | Employee Stock Option (right to buy) | Award | 523.5% | 445,000 | 530,000 | 09 Mar 2026 | Direct | |||
| Mark Wayne Peres | Employee Stock Option (right to buy) | Award | 557.5% | 223,000 | 263,000 | 09 Mar 2026 | Direct | |||
| Jonathan H. Gordon | Employee Stock Option (right to buy) | Award | 212.4% | 223,000 | 328,000 | 09 Mar 2026 | Direct | |||
| William A. Schmitz | Employee Stock Option (right to buy) | Award | 22755.1% | 223,000 | 223,980 | 09 Mar 2026 | Direct | |||
| Jonathon Angell | Restricted Stock Unit | Award | 3.33% | 3,334 | 103,334 | 09 Mar 2026 | Direct | |||
| Leslie Goldman Tepper | Restricted Stock Unit | Award | 3.33% | 3,334 | 103,334 | 09 Mar 2026 | Direct | |||
| Thomas S. Glanville | Restricted Stock Unit | Award | 3.33% | 3,334 | 103,334 | 09 Mar 2026 | Direct | |||
| Mark Wayne Peres | Employee Stock Option (right to buy) | Award | 15,000 | 15,000 | 19 Feb 2026 | Direct | ||||
| Mark Wayne Peres | Restricted Stock Unit | Award | 25,000 | 25,000 | 19 Feb 2026 | Direct | ||||
| Michael Allen Brasel | Employee Stock Option (right to buy) | Award | 15,000 | 15,000 | 18 Feb 2026 | Direct | ||||
| William Mark Schmitz | Employee Stock Option (right to buy) | Award | 15,000 | 15,000 | 18 Feb 2026 | Direct | ||||
| Jonathan H. Gordon | Employee Stock Option (right to buy) | Award | 20,000 | 20,000 | 18 Feb 2026 | Direct | ||||
| Blake Janover | Restricted Stock Unit | Award | 100,000 | 100,000 | 19 Dec 2025 | Direct | ||||
| Elizabeth Muller | Restricted Stock Units | Award | 549,451 | 549,451 | 09 Dec 2025 | Direct | ||||
| Elizabeth Muller | Stock Option (right to buy) | Award | 22.6% | 183,150 | 994,849 | 09 Dec 2025 | Direct | |||
| Thomas S. Glanville | Restricted Stock Unit | Award | 100,000 | 100,000 | 12 Nov 2025 | Direct | ||||
| Jonathon Angell | Restricted Stock Unit | Award | 100,000 | 100,000 | 12 Nov 2025 | Direct | ||||
| Tepper Leslie Goldman | Restricted Stock Units | Award | 100,000 | 100,000 | 12 Nov 2025 | Direct | ||||
| Michael Allen Brasel | Employee Stock Option (right to buy) | Award | 70,000 | 70,000 | 07 Nov 2025 | Direct | ||||
| Jonathan H. Gordon | Employee Stock Option (right to buy) | Award | 85,000 | 85,000 | 07 Nov 2025 | Direct | ||||
| Richard Muller | Common Stock | Award | 5,196,426 | 5,196,426 | 05 Sep 2025 | Direct | ||||
| Elizabeth Muller | Common Stock | Award | 5,057,855 | 5,057,855 | 05 Sep 2025 | By Muller Family Trust | ||||
| Elizabeth Muller | Common Stock | Award | 5,196,426 | 5,196,426 | 05 Sep 2025 | Direct | ||||
| William Mark Schmitz | Common Stock | Award | 103,928 | 103,928 | 05 Sep 2025 | Direct | ||||
| Mark N. Tompkins | Common Stock | Other | -60% | -2,833,333 | 1,891,667 | 05 Sep 2025 | Direct | |||
| Mark N. Tompkins | Common Stock | Sale | -0.53% | -25,000 | 4,725,000 | 26 Aug 2025 | Direct | |||
| Ian Seth Jacobs | Common Stock | Purchase | 10% | 25,000 | 275,000 | 26 Aug 2025 | Direct |
* marks a reported price that did not pass the local price check.