Cells form from pre-existing cells. This is one of the fundamental principles of cell theory, which states that:

* All living things are made up of cells.

* Cells are the basic unit of life.

* All cells arise from pre-existing cells.

This means that cells don't spontaneously generate from non-living matter. They are produced through a process called cell division, where an existing cell divides into two or more daughter cells.

There are two main types of cell division:

* Mitosis: This type of division produces two identical daughter cells, each with the same number of chromosomes as the parent cell. It is used for growth, repair, and asexual reproduction.

* Meiosis: This type of division produces four daughter cells, each with half the number of chromosomes as the parent cell. It is used for sexual reproduction.

So, in short, cells are not formed from scratch but rather arise from the division of previously existing cells.