This play handbook appears during a challenging period in the historical development of early childhood. There is growing evidence concerning the general importance of play in early childhood development of animals and humans. At the same time surveys show that advanced forms of human play are disappearing from different societies. It has been difficult to demonstrate cultural consequences of the disappearance of play on general psychological development, but animal experiments indicate changes in the brain architecture of non-playing individuals. In this book a chapter replicating El’konin’s survey study carried out fifty years ago showed a remarkable drop in children’s pretend play. In human children less advanced play might be a factor behind lower level of self-regulation.