Lesson 1: What is a cell?

A cell is the smallest unit of life. Your body is made of trillions of cells, and each one carries out the work that keeps you alive.

A round cell with a dark nucleus in the centre, surrounded by cytoplasm and a thin outer membrane. — Figure 1. The three main parts of an animal cell.

The three main parts

Membrane: The thin outer layer that controls what goes in and out.
Cytoplasm: The jelly-like fluid where most of the work happens.
Nucleus: The control centre that holds the genetic instructions.