DNA transformation is a naturally occurring but rare event in which DNA can be transferred into bacteria. In 1970, Morton Mandel and Akiko Higa discovered a way to make E. coli more 'competent' for transforming foreign DNA. Their calcium chloride method is widely used today to obtain high-efficiency transforming cells. This animation from Cold Spring Harbor Laboratory's Dolan DNA Learning Center presents the second part of explaining DNA transformation through a series of illustrations of the processes involved.