View full lesson: http://ed.ted.com/lessons/how-do-your-kidneys-work-emma-bryce

After drinking a few glasses of water on a hot day, you might be struck with a sudden ... urge. Behind that feeling are two bean-shaped organs that work as fine-tuned internal sensors. Emma Bryce details how the incredible kidneys balance the amount of fluid in your body, detect waste in your blood, and know when to release the vitamins, minerals, and hormones you need to stay alive.

Lesson by Emma Bryce, animation by Tremendousness.