Charles Langmuir is Professor of Geochemistry and Director of the Mineralogical Museum at Harvard University. He studies diverse aspects of volcanism at ocean ridges and convergent margins. He has received the Bowen Award, Holmes Medal, and Urey Medal and been elected to the NAS and AAAS. He was principal investigator for PetDB, and one of the founders of the G-cubed journal. With Wally Broecker he has written How to Build a Habitable Planet, the story of Earth from the Big Bang to humankind.