There is a baby like 2 years old. Not my child, a friend's child. He's completely insane, to the point where someone has to follow him when they come to visit to make sure he doesn't destroy anything. But I noticed that at some point he really started to focus on the jar with the tennis balls - shaking the balls every now and then, putting them back down and closing the jar again and again. It was the most peaceful thing I've ever seen. It occurred to me that some nesting dolls might be a good present for him. When I received the dolls I couldn't open the first one so I just threw it in the trash (I wrapped a lot of Christmas presents at the last moment - no time to play around). My brother was there. He's a rather masculine guy, and grip strength correlates strongly with testosterone, so he pulled them out of the trash, opened them up, and sanded the inside and outside edges of each doll with coarse sandpaper (if you get the impression these things are plastic, they're so messed up, made of wood, and they're not very big.) So now everyone thinks I'm a genius, the next Temple Brandon. The toddler shakes the dolls, realizing there is something inside, and opens them until they can't go any further, then puts them back together and then shakes them. Washes and repeats. money well spent.