Embryonic stem (ES) cell culture basics. 
This unit describes the procedures to grow and maintain embryonic stem (ES) cells in culture.  Growth-inactivated mouse embryo fibroblasts (MEF) are required as a feeder layer for the ES cells; their isolation and culture is described as are the additional protocols required for generating a mouse with a particular targeted gene electroporation, cloning and selection for homologous recombinants, transfection with Cre, and preparation of cells for injection.