This is probably my very favorite thing little kids do. The younger the child the better. I love when they belly up to the floor and play. He was in the music room, on his belly, lining up frogs for thirty minutes. He would come and get me because he was so proud of his work. Dominic lined up animals at this age. John and I would take pictures of his line ups at night after he went to bed. What was cute about Dominic's line-ups is that we would find them all over the house. It was so great.