In one of my library runs I ran into this tiny book (by the way, this 24-page book sells for more than $150 US dollars now, heavenly price, but you can borrow from the library), so thin that I wouldn't even have seen it if not for that it's sitting right next to the book I took out.
The book is Christine Brown's annotations to (another of) Bartók's piano album written for children. He wrote it initially to teach his son, which turned out to have happened only for a short duration, but he finished the book anyway, with 153 small pieces that some regard as Bartók's finest works in teaching.
The word Mikrokosmos means "little world", micro cosmos :) I think Bartók rocks the hardest problem of the world - naming things.
The book starts with very basic things, like unison melodies, I assume that's a pianists' counterpart to our open strings. Then it slowly adds more materials such as syncopation, change of position, imitation and counterpoint, etc. And then, some concept would come back again with more complexity.
Fine work like this makes me feel if one day I gonna properly learn to play the piano (to reasonable extent), I have a path.