Cell differentiation is defined as a process, by which less specialized cells, such as embryonic cells become more specialized. The process of cell differentiation is regulated by gene expression. Gene expression involves a specific group of genes that are turned on (expressed) or turn off (repressed) and dictates a cell's function.
A fertilized egg represents a single, non-specialized cell that develops into a complex, multicellular organism by cell differentiation. Thus, a adult rabbit looks so much different as compared to a single fertilized cell or zygote, due to cell differentiation, which is regulated by gene expression.
