Why is blood red?

Blood is red because it has lots of tiny red cells called red blood cells. Scientists also call them erythrocytes.

Here is an easy way to think about it:

• Red blood cells are like little red trucks that drive all through your body.
• Each truck carries a special red helper called hemoglobin. Hemoglobin has iron, and that makes it look red.
• Hemoglobin picks up oxygen in your lungs (like picking up a passenger) and drops it off where your body needs it (like making a delivery).

So blood looks red because it is full of those red trucks filled with hemoglobin.

Fun fact: The big word "erythrocyte" just means "red cell."