While plenty of baby toys come with audio recordings, flashing lights and an abundance of moving parts, you can get lots of developmental mileage out of very simple toys. Such is the case with a simple box that has a hinged door. This may come in the form of a play oven or a small chest. You can even use a small, heavy-weight cardboard box with flaps.
For starters, boxes allow infants to pull themselves up, prop themselves up, and lean on something sturdy when their legs are less than sturdy. This helps in the development of motor skills, balance and physical strength -- all of which come in handy when a baby works up to his or her first steps.
Next we'll take a look at the spitting image of infant development.