called tartrazine or "yellow no. 5," that makes the technique possible. The trick is to mix it into a solution of water and rub it onto the shaved skin of a mouse. And voilà: you've got a ...

The dye is a food colouring called tartrazine ... whether the process would work on humans, whose skin is 10 times as thick as that of a mouse. It might be possible to use more dye or deliver ...