It’s an amazing thing to see your baby grow.

Marcel, for instance, is in the middle of spurt that’s making her taller than everyone else in her class. Of course, we see the most growth in Tristan, who turns 11 months old, soon. Her growth isn’t just size, though. Her growth is also in strength.

The most shocking growth in strength was her crawling.  Marcel never crawled. Instead, she would, while in a kneeling position, hop whereever she wanted to go. Then, fourteen months into life, she started walking.

The most remarkable growth, though, isn’t physical. It’s mental.

Marcel started reading this week. She can’t read sentences. But she can pick out words that repeat in a story. She picked out the words “scrub” and “row” from Sandra Boytons’ “The Going to Bed Book” and the words “daddy” and “cuddles” from Gutmen’s and Hallensleben’s “Daddy Cuddles.” I have looked forward to the day I taught my children to read since before–long before–I even had children, so this was huge for me.

What I didn’t expect to be even more amazing and more huge to me was the day that Tristan learned to play.

A few months ago, Tristan was sitting in her high chair, drinking from her bottle, when she got bored and threw that bottle on the floor. Marcel retrieved it and returned it to Tristan in her high chair, then went back to what she was doing. Tristan, however, simply threw it, again.

Marcel, again, got up, retrieved it and went back to what she was doing but, this time, went back with one eye looking over her shoulder at Tristan. Tristan, again, started to throw her bottle but, this time, she waited for Marcel to come back to her.  When Marcel came back, Tristan smiled and dropped the bottle at the feet of the waiting Marcel.

And thus, Tristan, for all she knew, invented the game of “catch” and taught her big sister how to play.

It was an amazing milestone to behold.