"We think we've found a common factor in the movement of embryonic cells during development and of cancer cells during the spread of the disease, " said Professor Stern.

BBC: NEWS | Health | Molecule 'helps cancer to spread'

That discovery has cast light on human embryonic development and, indeed, on the everyday working of adult bodies.

ECONOMIST: The 2002 Nobel prizes: Windows on the world | The

To solve the mystery, Dr Kandel, and his colleague Kausik Si, turned to embryonic development.

ECONOMIST: Prion proteins