Cell Structure

According to the cell theory (which is certainly correct), every living organism - plant, animal, or otherwise - is made of cells, and all cells arise from pre-existing cells.

The simplest organisms, like amoebas and bacteria, are made of only one cell; in other words, they are unicellular. Complex organisms such as plants, fungi, and humans and other animals are made up of many, many cells; in other words they're multicellular.

Look at the following diagram, and think of a cell as having three main areas:

1) the cell wall and/or membrane, which forms the outer layer,

2) the cytoplasm, in which the organelles are found, and

3) the nucleus, which is bounded by a nuclear membrane, and in which chromosomes are located.