Thomas Hunt Morgan was not directly involved in developing cell theory. His contributions were primarily in the field of genetics, specifically through his work with fruit flies (Drosophila melanogaster).

Here's how Morgan's work impacted our understanding of cells and inheritance:

* Chromosomal theory of inheritance: He proved that genes are located on chromosomes, which are structures found within the nucleus of a cell. This discovery was a major breakthrough in understanding how traits are passed down from parents to offspring.

* Genetic mapping: Morgan mapped the relative positions of genes on chromosomes by studying how often they were inherited together. This led to the development of genetic maps, which are still used today to understand the organization of genomes.

* Mutations and evolution: Morgan's work with fruit flies also helped to demonstrate the role of mutations in evolution. He showed that mutations could lead to new traits and that these traits could be passed on to offspring.

While cell theory was already established by the time Morgan began his work, his discoveries significantly expanded our understanding of the processes happening inside cells and how these processes contribute to inheritance and evolution.

In essence, Morgan's work built upon the foundation of cell theory by demonstrating the complex workings of chromosomes and their role in transmitting genetic information.