The LUMA digital bath thermometer activates automatically as soon as it touches the water. It floats, allowing you to see the display at all times. Blue means too cold, red means too hot, and green indicates just right. In addition to the color indicator, you can read the exact temperature of the water. The thermometer automatically turns off after use. It is also easy to clean: simply remove the cap, wipe it with a cloth, and it's clean. It's that simple; when the display is green, you can bathe your baby.