Geometry
Lincoln has a truly awful set of blocks that he plays with. Actually, he only plays with them on me. Technically, on my face. 12 square rubber squeaky blocks that he stacks on my forehead and then smashes the tower down on my face. I hate those blocks. I hide them whenever I put them away until Mommy tracks them down and Lincoln can then resume the reign of terror on my face.
Tonight he broke out the block collection and climbed into my lap. Instead of the typical round of "smash daddy's face," we started using the blocks to explain maths (1 x 12, 2 x 6, 3 x 4, etc.) and to build different structures. I made a cube and showed him how it was 2 x 2 x 2 and square on all sides and then explained that the Borg fly around in cubes and when the flying cube crashed into him, he had been assimilated and now he was a Borg, too. He told me he didn't want to be a Borg, but I told him resistance is futile.
Look, Mommy isn't going to teach him these things. He's going to be three this year. He needs to know.