Regulation of gene expression is intimately connected to post-translational modification of histones bound to DNA. One important type of modification is acetylation of lysine residues of the N-terminal "tails." Because of the central role that covalent modifications like acetylation play in gene regulation, it is no wonder that there has been considerable interest directed towards identifying and characterizing the enzymes that catalyze these modifications. The MYST family is the largest but, until recently, one of the least well studied families of histone acetyltransferases. Experiments performed in the last few years show that MYST family proteins have a fascinating and diverse range of functions affecting almost all cellular phenomena. MYST family proteins have central and specific roles in regulating cellular processes ranging from apoptosis, cell cycle and adult stem cell homeostasis to patterning of the early embryo. Since these are fundamental cellular processes it is not surprising that mutations in MYST genes are also associated with pathological conditions such as leukemia.