You could think of any regular / irregular shape when you just have a dot with you, but not decide or command on what would be the end shape.
A cell could have evolve has anything, for its correct to say that end product has evolved from a cell and not a cell would evolve into this particular end product.
Had we have the right to say that any cell would transform to this particular shape, then what is the need to have so many patterns or why is the diversified nature of these patterns we see ?
So, its the egg that is as the input for to proceed, transform and arrive at another product
( I suppose I had selected ' Egg Came first ' )