The way my first son moved in utero, I swore he'd be kickboxing at birth. Of course, like every newborn, all he could do in those early days was flail his tiny arms and legs. His head was so wobbly that if I held him upright in front of my chest, it would bob and weave before finally dropping onto my shoulder.
Babies have a long way to go before they can toddle swiftly across a room. To accomplish each motor milestone -- whether it's grasping, rolling over, or walking -- an infant needs the right mix of muscular strength, balance, coordination, cognitive development, and, especially, desire. Fortunately, "children have an incredible quest for mobility that helps them pull up against gravity and get on their feet," says Gordon Williamson, Ph.D., an associate clinical professor in the rehabilitation medicine department at John F. Kennedy Medical Center, in Edison, New Jersey. Each physical skill your child conquers becomes a building block for the next, and you can do a lot to help move things along. Follow our guide to the milestones your baby will master in the first 18 months of life. (Age ranges are approximate.)