Talking?!?

For quite a while Bogdan has had a very few words that he says and a few that he signs. He understands what is going on around him, but really doesn't say much. He does discourse with all kinds of expression, intonation and gesturing, but all with his mouth closed, just making noises in his throat. It's really cute, but hard to explain. And it's definitely not anything we can understand. Then, yesterday he started saying a very clear "nyet" except that it's missing the T on the end. Just now, Jaan went outside, and Bogdan was left behind. Bogdan went to the door and yelled, "Jaa! Where are you?" ("Я! Де ты?") His first sentence!