The document provides information about cell structure and function. It defines cells as the basic building blocks of living things and notes they are only visible under a microscope. The main components of a typical cell are described including the nucleus which houses DNA, organelles such as mitochondria and lysosomes, and the cell membrane. The cell membrane is made of a phospholipid bilayer with proteins embedded throughout, allowing for selective control of what enters and exits the cell. This fluid mosaic model of the cell membrane is described in detail.