Embryonic stem (ES) cells are pluripotent cells isolated from the inner cell mass of the pre-implantation blastocyst. They have the capacity to undergo indefinite rounds of self-renewing cell division and differentiate into all the cell lineages of the developing embryo. In suspension culture, ES cells will differentiate into aggregates known as embryoid bodies in a manner similar to the early embryo. This culture system therefore provides a useful model to study the relatively inaccessible stages of mammalian development. We describe methods for the routine maintenance of mouse embryonic stem cells in culture, assays of stem cell self-renewal potential in monolayer culture and the generation of embryoid bodies to study differentiation pathways.
