Getting ready to crawl?

I have really enjoyed "the slug stage" where Addi hasn't really be able to move very far. She sits and scoots a little. Mostly, she's pretty content. If she can't reach a toy, she just moves onto something else. Tonight, I put her down on her tummy after her bath. I looked down and she was on her knees. I congratulated her and took as many pictures as possible. These would be great in a picture flip book. I'm afraid this is the beginning of the end of her not moving...we need to get gate...hmmm!