A pyramid is a massive stone structure with a square base and four triangular sides that meet at a point at the top. The ancient Egyptians built the most famous pyramids as tombs for their pharaohs over 4,500 years ago. The largest, the Great Pyramid of Giza, took roughly 20 years to build and required moving over two million stone blocks, some weighing as much as a car.

Building a pyramid demanded incredible organization and mathematical precision. Workers had to cut stone blocks to exact sizes, transport them without wheels or pulleys, and stack them perfectly so the structure wouldn't collapse. The pyramids still stand today, which tells you how skilled these ancient builders were.

In geometry, a pyramid is any solid shape with a flat base and triangular sides meeting at a point, called the apex. A square pyramid looks like the Egyptian monuments, but pyramids can have triangular, pentagonal, or other polygon bases too.

People also use pyramid to describe how things are organized by levels. A food pyramid shows which foods to eat more of (at the wide bottom) and less of (at the narrow top). In sports, you might see cheerleaders form a human pyramid, with more people on the bottom level supporting fewer people above.