The statement that all cells come from pre-existing cells is part of the Cell Theory.

The Cell Theory is one of the fundamental principles of biology, and it states that:

1. All living organisms are composed of one or more cells.

2. The cell is the basic unit of structure and organization in organisms.

3. All cells arise from pre-existing cells.

This theory was developed over time by several scientists, including Robert Hooke, Antonie van Leeuwenhoek, Matthias Schleiden, Theodor Schwann, and Rudolf Virchow.