Blocks

Sofi has a toy where you slide blocks of different shapes into a box with holes of different shapes - you're supposed to match the blocks with the holes. It used to be the only ones she could get in where the cylinders - because it didn't matter which orientation you tried to stuff them through the holes.
Yesterday I was watching her play with it and she clearly Got It - I'm not sure when she figured it out, but now she knows which block goes through which hole, and if she has trouble getting the orientation right, she'll pull back, adjust her grip, and then try again.
I suppose non-parents think, "Yeah, great Jamie, she can put blocks in holes." There's something about seeing your baby do something - anything for the first time that's just so awesome.