Embryonic stem (ES) cells are increasingly providing their value, not only in research aimed at understanding gene gunction and human disease, but also as a potential means to treat these diseases. This volume is designed to be a practical guide for the rapidly growing researchers in this field. Details are provided on how to culture, transfect and differentiate established cell lines, and how to isolate new cell lines. Gene targeting experiments are described for anumber of cell types, and include protocols for gene-targeting vectors, DNA transfection and RNA interference.