The Foundation of Life

Cell theory is one of the fundamental principles of biology. It consists of three core tenets:

1. All living organisms are composed of one or more cells
2. The cell is the basic unit of structure and function
3. All cells arise from pre-existing cells

The discovery of cells began with Robert Hooke in 1665, who observed cork under a microscope and coined the term "cell." Later, Anton van Leeuwenhoek observed the first living cells.

There are two major types of cells, distinguished by their structural organization:

Eukaryotic cells contain specialized structures called organelles, each with specific functions:

Cellular respiration is the process by which cells convert glucose into ATP — the energy currency of all living cells.