The statement "cells only come from preexisting cells" is a fundamental principle in biology known as cell theory. While it's difficult to pinpoint a single person who definitively "said" it, the credit for its formulation is usually attributed to Rudolf Virchow, a German physician and pathologist.

Here's why:

* Virchow's famous quote: Virchow is best known for his phrase, "Omnis cellula e cellula" (Latin for "all cells arise from cells"), which he published in 1855. This statement encapsulated the concept of cell theory, building upon the work of earlier scientists.

* Earlier work: While Virchow's statement is iconic, other scientists contributed to the development of cell theory. Robert Hooke first observed cells in 1665, and Antonie van Leeuwenhoek made significant contributions to the understanding of microscopic organisms.

* Collaborative nature of science: It's important to remember that scientific discovery is often a collaborative process. Virchow built upon the work of his predecessors, and his contributions were refined and expanded upon by later scientists.

So, while Virchow is often credited with popularizing the phrase, it's more accurate to say that cell theory emerged from the work of many scientists over time.