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Hey, Brain Stuff. Lauren Vogelbaum here.

Red elicits strong reactions.

Around the world, it is by far the most commonly used color in national flags.

It can be a major confidence booster.

Researchers have found that wearing red garments makes people feel more attractive.

On the flip side, according to one study from 2013, looking at red things might cause us to experience pain more intensely.

Maybe red wouldn't provoke our brain so much if it didn't happen to be the color of human

blood. In this regard, homo sapiens is far from unique. From timber wolves to tiger sharks,

most vertebrate animals have crimson-colored blood in their veins.

This hue is produced by hemoglobin, the protein that helps our blood distribute oxygen around

our bodies. In grade school, you probably learned that blood contains three types of cells.

White blood cells help us fight off viruses, harmful bacteria,

and other pathogens. Then we've got platelets, the damage control specialists, that allow our blood to clot.

Last but certainly not least, we've got red blood cells. Their main purpose is to carry around

oxygen from and take away carbon dioxide to the lungs, where these

gases are inhaled and exhaled respectively. The protein hemoglobin lets these cells execute both

tasks. A core ingredient in red blood cells, hemoglobin combined to oxygen and carbon dioxide.

Hemoglobin is partly made up of iron atoms,

which give this protein, and by extension, are red blood cells, a crimson color. Since our platelets and white blood cells are vastly outnumbered by red blood cells, human blood as a whole

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