Every Agatha Christie detective novel that has entered the United States public domain, set for reading on a phone, with a companion that has only read as far as you have. The interesting problem was not the typography. It was building an assistant that knows the whole book and can be trusted not to tell you.

Every supplement, drug, procedure and behaviour the longevity industry sells, graded against the human evidence that actually exists. Most turn out to be untested rather than disproven — and the grading was done by having two AI models audit the literature and argue with each other until they ran out of objections.

Yamanaka's 2006 discovery showed cell identity is reversible. Today's bet is that you can wind a cell halfway back, recovering youth without erasing identity. The biology of partial reprogramming, the four-billion-dollar race to commercialize it, and what a real win looks like.