C. elegans cell lineage, circa 1981

Starting in 1980, John Sulston spent 18 months hunched over a microscope watching Caenorhabditis elegans embryos divide. Together with Bob Horvitz at the Laboratory of Molecular Biology in Cambridge, England, he had already mapped the fate of every cell in the adult worm from the moment the egg hatched, but the embryonic cell lineage remained elusive. Many labs had tried and failed to study the developing embryos using photography, so Sulston figured he would do it by hand. "We all felt that there would be a way [to use photography] someday, but we needed the information now," he says.