Why do brain tissues have different colours? Can I train plasticity? Can I learn from a text by listening to it while I sleep?  Why do Dutch people say “I have sawdust in my head” when they do something stupid? Why do some people remember their dreams and others do not? Are emotions experienced in the heart or the brain? Why do some people remember things better than other people? Do we only use 10% of our brain? How is it that some people see an object as blue, while others say that same object is green? Why is sleep so essential?