ELI5: Explain Like I'm 5

Oxygen

Oxygen is a gas found in the air around us. It is mostly invisible, but it's very important because every living thing needs oxygen to stay alive. Your body needs oxygen to help it make energy and to keep you healthy. Each time we breathe, oxygen is delivered to our lungs and into our blood. The blood then transports the oxygen to every cell in our body, where it helps us to stay alive.