To use this toy, simply push the engine along like a regular toy train to recreate railway stories. To see the color - changing magic, put the engine in water. You can change the water temperature from warm to cold and back again to reveal hidden decorations. Make sure to dry the engine thoroughly after using it in water to prevent rust. Store it in a dry place when not in use. Also, since each engine is sold separately, availability may vary, so grab your favorite character while you can.