There are more than three states of matter
Your blood isn't blue when its oxygen is depleted
You have more than five senses
Your tongue doesn't have a taste map
Hair and fingernails don't continue to grow after a person dies
ROYGBIV is not the lineup of colors in the rainbow

There are more than three states of matter

You may have learned about three—liquid, solid, and gas. Those are the most common states of matter that we find here on Earth, but beyond our atmosphere, there's a fourth state—plasma—and it might be the most common in the universe. When you add enough energy to an atom, its electrons can get away from its nucleus and react with a different nearby nucleus, creating plasma, which consists of highly charged particles with very high kinetic energy. Gases like neon are goaded into a plasma state by electricity to make glowing signs; stars are basically huge balls of plasma. But that's not the only extra state of matter: In 1995, scientists created one called the Bose-Einstein condensate, where matter is super-cooled to almost absolute zero, causing molecular motion to practically stop. Nobody knows whether Bose-Einstein condensates exist in nature, but they can be made in a lab. Researchers are also investigating other states of matter, so the number could keep growing, according to Gizmodo.

Your blood isn't blue when its oxygen is depleted

When you look at the inside of your wrist, the veins sure might look blue, but the truth is that the blood inside is red, according to Live Science. The veins appear to be blue because of the way your skin and tissues distort the light that's reflected back to your eye. We're also conditioned to think of veins returning oxygen-poor blue blood to our hearts because that's the way anatomical drawings traditionally look. But that's just to make differentiation easier—the blood is red when it's full of oxygen in our arteries, and it's still red (though darker) when the oxygen has been depleted and it's traveling back to our hearts through veins: Iron-rich hemoglobin gives it that color. Other animals, including horseshoe crabs and squid, do have blue blood, however, because the chemical that transports their oxygen contains copper. There are animals out there with green and even clear blood.

You have more than five senses

The big five—touch, taste, smell, sight, and hearing—are our most basic senses, but we're taking in information through a wealth of other mechanisms. Proprioception tells us where our bodies are in space, allowing us to stay balanced, according to Live Science. Kinesthetic receptors detect stretching in muscles and tendons, which helps us keep track of our various body parts. We also have receptors to keep track of how much oxygen is flowing through our arteries.

Your tongue doesn't have a taste map

Did you learn about a "taste map" when you were a kid? It's hooey, apparently, writes University of Florida professor Steven D. Munger in the news website The Conversation. The receptors that detect sweet, salty, sour, bitter, and umami are evenly distributed all over your tongue. The taste map grew out of a graph published by a German scientist in a paper in 1901—it was an imprecise representation of his experimental findings, but others took it literally and expanded on it during the decades that followed.

Hair and fingernails don't continue to grow after a person dies

Once oxygenated blood stops circulating at death, the cells that produce new hair and fingernail tissue can no longer function. The idea that hair and nails keep growing is a misinterpretation of what actually happens to a corpse in the hours and days after a person dies, according to the BBC. The skin dries out and retracts at the fingertips, making nails look longer. Men's facial skin also gets dehydrated, which can extend stubble and make it appear to have grown longer.

ROYGBIV is not the lineup of colors in the rainbow

You probably remember learning the "ROYGBIV" initialism to represent the colors of the rainbow: Red, Orange, Yellow, Green, Blue, Indigo, and Violet. Today, though, everyone from teachers to color specialists have begun to forego indigo. The rainbow LGBT Pride flag also only has six colors—and many people are left to wonder why indigo, which seems to be just an arbitrary combination of two of the other colors (blue and purple/violet), found its way into the rainbow. Well, for that we can thank Sir Isaac Newton, a superstitious sort who believed that the number seven had a cosmic significance, per occult beliefs of the time. So he believed that seven colors, no more, no less, had to come together to make white, and chose indigo to join the other colors, potentially because of the popularity of indigo dye at the time.