Give an example of changes that occur during differentiation in a multicellular organism

Cell differentiation or cellular differentiation refers to the procedure via which a cell goes through the modifications in gene expression to turn into a more unique kind of cell. It is the procedure where the cell modifies from one cell type to another, generally, the cell changes into a more unique kind.  

The procedure of cell differentiation permits the multicellular species to develop specifically functional kinds of cells and body plans. The process of cellular differentiation allows the formation of tissues as distinct as muscle and brain tissue from a single cell.  

the principles and empirical processes of discovery and demonstration considered characteristic of or necessary for scientific investigation, generally involving the observation of phenomena, the formulation of a hypothesis concerning the phenomena, experimentation to test the hypothesis, and development of a conclusion that confirms, rejects, or modifies the hypothesis.