Organisms are generally made up of cells. This is a fundamental principle of biology known as the cell theory. Here's why:

* Basic unit of life: Cells are the smallest units that can carry out all the processes necessary for life.

* Structure and function: Every organism is built from cells, and the specific types of cells and their organization determine the organism's structure and function.

Exceptions:

* Viruses: Viruses are not considered living organisms because they lack the ability to reproduce independently and rely on host cells to carry out their functions. They are essentially genetic material encased in a protein coat.

* Prions: Prions are infectious agents composed only of protein, lacking any genetic material. They can cause serious diseases by disrupting normal protein function.

So, while there are some exceptions, the vast majority of organisms are made up of cells. This concept is crucial to understanding biology and the complexity of life.