Well, this is because of a process known as cell differentiation. And what cell differentiation is? It's when a single precursor stem cell basically divides and produces differentiates into many different types of cells. And a great example of this differentiation process is our immune system. We know that our immune system consists of many different types of cells that have not only different structures and different sizes but also have their own unique function. So we have this single stem cell known as the hematopoietic stem cell that produces red blood cells and white blood cells.