Most Americans live in a state where medical marijuana, in some form, is legal. But all marijuana isn’t the same. Different plants have different chemical compositions, and different compositions are better at treating different diseases.

Enter Chris Hudalla. Hudalla studies cannabis to help home growers treat seizures, multiple sclerosis, migraines and other illnesses. The latest film in ESPN Films and FiveThirtyEight’s series “The Collectors” is “Cannabis Chemist,” directed by Jamie Schutz.