The science of snot and phlegm

Breathe in, breathe out ... We all do it, every day and every night. Breathing is essential for life. It brings oxygen (a gas in the air) into our lungs. We need oxygen to keep our brains and bodies working properly. Without it--without breathing--we would die very quickly! This breathtaking guide to breathing explores the process of breathing and how disgusting substances like mucus and snot have unexpected uses.