Why is cell called the structural unit of life?

Cells are called the structural unit of life because all living organisms are made of cells - from single-celled bacteria to complex humans with trillions of cells! Think of cells as the building blocks of life, similar to how bricks are the basic units of buildings. Every function in your body - breathing, digestion, thinking - ultimately happens at the cellular level. Whether an organism has one cell or billions, the cell represents the smallest living structure that can perform all life processes independently. This fundamental understanding forms the basis of modern biology!

The cell theory established in the 19th century states that: 1. All living things are composed of cells 2. The cell is the basic unit of structure and organization 3. All cells come from pre-existing cells

We call cells the structural units because they're the smallest entities that can be considered alive. Even in complex organisms like humans, tissues and organs are just organized collections of specialized cells working together. The cell membrane provides a distinct boundary, and inside, all the machinery of life (DNA, organelles) works to maintain homeostasis. Pretty amazing when you think about it!