OIST from Onna Village, Japan · CC BY 2.0

A South African-born biologist who spent decades at Cambridge's Laboratory of Molecular Biology working on the genetic code, and who chose, almost alone, to build a scientific field around a previously obscure roundworm: Caenorhabditis elegans became the standard model organism for studying how genes control development, used by labs worldwide ever since. He shared the 2002 Nobel Prize in Physiology or Medicine with H. Robert Horvitz and John Sulston for that work, and later founded the Molecular Sciences Institute in Berkeley.