Over breakfast, Griffin begins to tell Kemp at length how he became invisible. He had been a medical student, but had dropped medicine and taken up physics. Griffin was a medical student at the same time as Kemp, but Griffin switched to physics because he was interested in light. We also learn that, after leaving London seven years previously, he earned a living and had access to experimental resources as a demonstrator in a college in Chesilstowe. He came up with a loose theory for how to make objects invisible, but needed to figure out a method to actually do it.

He discovered a formula of pigments that lowers the refractive index of a substance, allowing light to pass through it rather than being reflected or refracted. After experimenting with pigments for three years, he came upon the secret whereby animal tissue could be rendered transparent. He was continuously trying to hide his work from another professor. He thought that his professor Mr. Oliver might take the credit for Griffin's published theory.