The cellular origins of a precancerous condition called Barrett's oesophagus have been unclear. Tracking and analysis of epithelial cells at the affected site could shed light on the problem. See Letter p.529

A precancerous condition called Barrett's oesophagus is of much interest, because it arises when some cells of the oesophagus take on a new identity — a phenomenon known as metaplasia. If we could understand where these altered cells come from, we might hold the key to preventing oesophageal cancer. On page 529, Jiang et al.1 provide fresh insight into the cell of origin for Barrett's oesophagus.