 He did his post-doctoral training at Stanford University in Palo Alto, California, where he invented the colony hybridization screening technique for recombinant DNAs in David Hogness' laboratory.After coming to UCLA in 1975, Grunstein pioneered the genetic analysis of histones in yeast and showed for the first time that histones are regulators of gene activity in living cells.His laboratory's studies provided inspiration for the eukaryotic histone code and underlie the modern study of epigenetics.