The NUK® Warm & Cool Mist Ultrasonic humidifier has 5 pre-programmed settings that take the guesswork out of humidification and many other wonderful features to create healthy environment all day and all night long. Pre-programmed settings take the guess work out of humidity – select the right setting and go! Warm mist soothes and cool mist refreshes. Adjustable Auto-Off lets user chooses how long the device will run - no danger of device left on unattended. Digital Humidistat auto-adjusts performance based on desired humidity level. Virtually silent operation won't wake sleeping child. The soothing amber nightlight is better for sleep than blue or white nightlights, which depress production of the sleep hormone melatonin. Child-Resistant Plug Lock catches and holds the appliance plug so that child cannot easily tug it out of the outlet. Filter Free design means no replacing expensive filters. 3 year warranty.