Historian David Bodanis subtitled his best seller E = mc2 "A Biography of the World's Most Famous Equation." Like most biographies, it includes stories of its subject's ancestors. In this case, innovative thinkers whose groundbreaking experiments shaped Einstein's understanding of mass, energy, and light. Their pioneering efforts helped make Einstein's great epiphany possible. With Bodanis's permission, we've adapted excerpts of E = mc2 to assemble snapshots of these ancestors in this article from NOVA Online.