Models are important tools: they resemble, they mimic, they imitate something to a greater or lesser extent. How similar models are to the 'real thing' is usually a challenging  issue. And it's a big issue with stem-cell derived models of the human embryo.

These embryo models, models of the embryo's 8-cell stage, of the blastocyst or of the gastrula are emerging and they are ones that labs can use to characterize the molecular and physiologic events that take place during early embryogenesis. My story in Nature Methods about some of these embryo models is here. For this story, I spoke with Christine Mummery, a researcher in the anatomy and embryology department at Leiden University Medical Center. In this podcast, she talks about models of the blastocyst and the gastrula, about the updated International Society for Stem Cell Research (ISSCR) guidelines, and shares some thoughts about about what is involved when assessing a model. "If I'm claiming this is a liver cell, what does it have to show? And this is a tricky, tricky thing," says Christine Mummery.