1. Ballpoint pens use rolling metal balls to write. Inside the tip of a ballpoint pen is a tiny, super-hard rolling sphere made of steel or tungsten carbide. As you drag the pen across paper, the ball rolls around, picking up thick ink from inside the reservoir and rolling it onto the page!

2. One single ballpoint pen can draw a line over a mile long. A standard BIC ballpoint pen contains enough ink to write about 45,000 words or draw a continuous line roughly 1.2 to 2 miles (2 to 3 kilometers) long before running out!

3. Space pens can write upside down and underwater. Standard pens rely on gravity to pull ink down to the tip, but Fisher Space Pens use pressurized gas cartridges to push thick ink out! This lets astronauts write in zero gravity, underwater, over grease, and in temperatures from -30°F to 250°F (-34°C to 121°C).

4. Early pens were made from goose feathers. Before modern factory pens were invented, people used quills—large feathers plucked from geese, swans, or crows! Writers carved a sharp point at the end of the feather stem and dipped it into a bottle of liquid ink every few words.

5. Ballpoint pens were invented to help airplane pilots. Liquid fountain pens leaked and sprayed ink all over high-altitude airplane pilots because of changing air pressure. In 1938, Hungarian journalist László Bíró invented a quick-drying, thick ink ballpoint pen that didn't leak in the sky!

6. Erasable pens use friction magic to hide ink. Modern erasable gel pens don't actually scrape ink off the paper when you rub them. They use thermochromic ink, which turns completely clear when heated up by the friction of the rubber eraser rubbing against the page!

7. People click pens billions of times a year out of habit. Studies show that pen clicking is one of the most common physical fidgeting habits in the world! The spring-loaded click mechanism was invented in the 1950s to extend and hide the ink tip without needing a removable cap.