Biology is the scientific study of life, derived from the prefix "bio-" (meaning life) and the suffix "-ology" (meaning the study of).

Life is highly diverse, existing in many forms from ocean life to plants and animals, but most life on Earth is microscopic and not visible to the naked eye.

The cell is the smallest, most basic unit of life, and the concept of the cell applies to all living organisms.

Unicellular organisms consist of a single cell, while multicellular organisms are made up of many cells.

Unicellular organisms are often only visible with a microscope, whereas multicellular organisms have specialized cells that perform different functions.

Key equation: Organism = Unicellular or Multicellular