Hemoglobin…possibly the most important part of our blood. It binds oxygen to transfer it from the air in the lungs to the body parts and binds to carbon dioxide and other waste to take it away to get rid of it through the lungs. The iron particles in the blood are the reason it appears red. Every animal discovered so far has this system, except one! The fish in the article below has clear blood and no hemoglobin. Insane!