As you probably know, all living things on the planet Earth are made up of cells.
When a group of cells come together to perform a specialized function, this collection is known as a tissue.
Things get really interesting when two or more tissues work together for the same purpose: this is an organ.
Organs are found in all living things such as animals and plants.
The organs inside our bodies are ticking away all the time, doing loads of different things to keep us alive.
However, you could survive pretty well without some of your internal organs.
You could live without your spleen, with only one of your lungs, with only one of your kidneys and with just 25% of your liver!
One of the organs which you really can’t do without is your heart, which beats away at an average of 72 beats per minute.
Your organs vary in the amount of energy that they use. Your brain uses 20% of your body’s energy, but only makes up 2% of its size.
On the other hand, your skin is the largest organ in your body but doesn’t use very much energy at all!