A bottle warmer is an electrical appliance designed for the safe and even heating of baby milk, beverages, or baby food. It usually operates on the principle of a water bath, where the bottle or jar with food is placed into a container of water, which the device heats to the desired temperature. This ensures gentle heating, preventing the formation of hot spots that could burn the child, and simultaneously helps preserve important nutrients in the food. Some models may also use steam for heating. Modern warmers often feature additional functions such as maintaining a constant temperature, defrosting frozen food, or sterilizing baby essentials.