A flea is a tiny jumping insect that lives by biting animals and drinking their blood. Fleas are so small you might barely see them, but they cause big problems. They make dogs and cats scratch constantly, and they can even bite people, leaving itchy red bumps on your ankles or legs.

What makes fleas remarkable is their jumping ability. A flea can leap about 150 times its own body height. If you could jump like a flea, you'd soar over a 60-story building in a single bound! They use these powerful jumps to hop from one animal to another.

Fleas have been pests throughout history. In the 1300s, fleas that lived on rats helped spread the Black Death, a plague that killed millions of people across Europe and Asia. Today, pet owners use special medicines to keep fleas off their dogs and cats. If you've ever seen a dog wearing a flea collar, that's what it's for.

The phrase flea market describes an outdoor market selling used goods and antiques.