1 | Sheldon | Glashow | American physicist who won a Nobel Prize in physics in 1950. |
| Paul | Cohen | American mathematician who won the Fields Medal in 1966. |
| Carl | Sagan | An American astronomer. |
| Mr. | Spock | A fictional character in Star Trek. |
| Hope | Jahren | Protagonist, narrator, and author. |
| | | The Jahren Laboratory - Hope's Laboratory. |
| Bill | | Hope's lab partner. |
4 | Pharm.D | | Hope's supervisor. |
| Lydia | | Hope's trainer. |
| Sydney | Ringer | A British physiologist. |
| Claude | | The lifer at the prison. |
| Mr. | Knauer | A meat seller. |
| | | ECT - Electroconvulsive Therapy. |
6 | Jean | Genet | A french novelist. |
8 | Buck | | Hope's only friend in Logan County. |
| | | Part Two - Woods and Knots |
2 | Reba | | Hope's chespeake bay retriever. |
| Professor | Santa | The Elf's Boss. |
4 | Stuckie | | Fossilized dog displayed in the museum Southern Forest World. |
| King | | The huge gorilla. |
5 | | | NSF - National Science Foundation. |
6 | | | Kudzu - A vine from the Phillipines. |
7 | Jackie | | A geriatric mare. |
| Karen | | The undergraduate lab assistant of Bill and Karen. |
10 | Teri | | Hope's graduate student. |
| Noah | | Hope's genius undergraduate assitant. |
| Cal | | A teacher / Hope's friend. |
| Linda | | Cal's wife / Hope's friend. |
| Olivia | | Cal and Linda's daughter. |
| | | Part Three - Flowers and Fruits |
2 | Ed | | Hope's favorite academic uncle. |
| Henrik | | A genius guy who formerly works for Ed. |
6 | Clint | | Hope's husband. |
| Sugar | | Hope's brown mare. |
| Walter | | The head of a department at John Hopkins. |
10 | Billy | | Lorna's co-proprietor. |
| | | Phoenix - A B-and-B Organic Farm. |
| Josh | | Bill and Hope's newbie. |
12 | Coco | | Hope's dog / Reba's successor. |
| Marge | Piercy | An American Poet. |
14 | Matt | | The Experiment leader of Hope's student. |