Close to crawling

This past week Rebecca started rocking back and forth on her hands and knees. At first it was just occasionally. Now it is every time I put her down on the floor, and often when I put her in her crib. She will move all four limbs at the same time, so that she falls flat on her tummy, but I know it won't be too long before she figures out how to coordinate her movements. I wonder if she will start crawling before she learns to sit!