Owing to its critical role in memory formation, the hippocampus is one of the most studied brain regions, yet how it arises from a single layer of cortical stem cells has been remarkably elusive. Two groups led by Monuki and Tole now show that the transcription factor Lhx2 has a key role in this process and confirm that the cortical hem, a medial telencephalic signalling centre, is actually a
... [Show full abstract] hippocampal organizer.