During World War II, engineer Richard James watched a steel spring roll and bounce, and decided it would make a good toy. The Slinky was born. This high-speed picture freezes the action of the spring as a boy flips it from one hand to another.

During World War II, engineer Richard James watched a steel spring roll and bounce, and decided it would make a good toy. The Slinky was born. This high-speed picture freezes the action of the spring as a boy flips it from one hand to another.