The zonal separation of proteins on the basis of net charge was initially conducted on paper, then in columns of sucrose and later in gels of starch and polyacrylamide, with appropriate electric fields. Then, in 1964, a graduate student at MIT discovered the power of sodium dodecyl sulfate (SDS) to dissociate the envelope proteins of Escherichia coli and to dramatically enhance their electrophoretic resolution when the detergent was included in the gel. While this Ph.D. thesis work continued, a group at the Albert Einstein College of Medicine published in 1965 the use of SDS to disrupt poliovirus particles and to resolve the proteins in gels containing SDS. This group soon followed with a publication (1966) on the application of this new method to the study of immunoglobulin heavy and light chain synthesis. Because of concurrent advances in gel filtration and other methods of protein separation, SDS gel electrophoresis had its greatest impact not in biochemistry but in cell biology and virology. Ingenious devices were soon introduced that facilitated the application of this method to radioactive protein mixtures, followed by the introduction of slab gels for the simultaneous resolution of multiple samples in parallel lanes in a single run. As we today routinely perform "SDS PAGE" (as the method become known, to the great irritation of journal copyeditors and nomenclature committees at the time), it is fitting to pause--four decades later, and remember the pioneers who made SDS gel electrophoresis a reality, a true milestone that caught on almost overnight.