Here is Matthew practicing his standing:
Then I caught a moment of excitement:
I'm a sucker for those blue eyes.
Then he decided the excitement was over, so he started trying to slide forward. He hasn't learned how to get very far yet, so he mostly just ends up on his back.
This isn't the best shot, but Matthew loves to get his socks off and wave them around and/or chew on them. This is an action shot of that celebratory dance: