Is there a cure for spots? Why do we cry? Does alcohol really kill brain cells? It's a Question and Answer Extravaganza on this week's Naked Scientists! We find out what makes a Chameleon change colour, why birds fly into windows and how a hair can change colour along it's length. Also, witnessing the birth of stars, the Neanderthal genome and how washing your hands can change the way you think. Plus, Meera dabbles with green gadgets and smell-free toilets in the home of the future, and Dave shows you how to build a hovercraft in Kitchen Science.