- from Cells
All living things have one thing in common—they’re composed of cells.
Cells are often described as “building blocks.” For instance, you are made of many trillions of cells. Yet cells are not just tiny bricks. Like you, each one gathers fuel, creates energy, grows, reproduces, and even dies.
Every cell also carries a complete set of instructions. In a plant cell, that set of instructions determines things like leaf size. In a tiger, it tells each cell in a stripe what color it is supposed to be. In a human cell, it gives us features such as height and eye color. It also decides whether an organism becomes a plant, a tiger, or a human. In other words, cells contain the master code that makes all living things what they are.