Researchers are now hard at work studying bivalent marks to see what they can tell us about pluripotency and differentiation. They could also be used to assess where a cell is at in its career, which would be crucial if stem cells are to be used for medical therapies. Rudolf Jaenisch of the Whitehead Institute for Biomedical Research in Massachusetts and his team recently used bivalent marks to show that they had successfully reprogrammed adult cells into a stem-cell-like state (see Wernig et al 2007).

So if you ever feel as though you can’t switch careers at your stage in life, then spare a thought for your cells because it seems that, with a little help, it’s never too late to change.