Topic description:
Using a synthetic system based on mouse Embryonic Stem cells, we have been able to recapitulate two key events of mammalian development: axial specification and elongation in culture. Surprisingly, and in contrast with the situation in the embryo, this happens in the absence of any input from tissues that interface with the mother. These observations lead to some considerations of how molecular and cellular systems interface in the specification and unfolding of axes in mammals.