Have you ever wanted to be something other than human? Mermaids, half human, half fish, are one of the most amazing mythical creatures. Best known for sitting on rocks, singing, combing their long, blonde, beautiful hair. Their tail's color is based on the mermaid's personality, and reflects their true feelings. Pretty cool, huh?
Every baby is different, but most will roll over at an age between 4 months and 6 months. Rolling from front to back can be done just by kicking, which babies are pretty good at by that age, but going from back to front requires a little more upper-body (neck, arm, etc) muscle development.
After gaining head control and right before (or about the same time as) coming to grips with sitting on their own, most babies learn to roll over. This skill is pretty self-explanatory - babies who have mastered rolling over can flip from lying on their back to being on their tummy and vice versa.