ID 298621361 © Artinspiring | Megapixl.com
Sharing is not just caring, it's also about giving credit - add this image to your page and give credit to the talented photographer who captured it.:
circadian vector rhythm sleep woman health balance day night time melatonin wakefulness flat person natural human character biological clock timing 24hour cycle routine adult arrow daily sun healthy phase schedule circle bedtime light lifestyle watch regulation period chronometer awake alarm sunlight hour dial timer hormone process internal life system black