Ericailcane's book Potente di Fuoco made me smile last night. My three children are budding artists (or architects) and doodling, drawing and designing are part of our daily life (one of the most appreciable aspects of coming home for lunch between 12-2!). Dylan was particularly prolific when he was young, and like many a mum, I have kept a lot (boxes!) of his artwork.
Leonardo's parents obviously did the same thing, saving and storing until the day they decided to give him back his first drawings and the idea for his book was born.
Potente di Fuoco is a collection of real and imaginary animals drawn in 1985 and 2009. The same creatures, the same artist, as a boy and a man. You can flick through it here.
It's an interesting idea, and one that you might like to keep in mind for your own kids, I know we certainly have enough material!