The physics and sequence of events behind the formation of galaxies, the remarkable structures in which most of the stars in the universe reside, has remained a long-standing puzzle. Now that we have a quite definite cosmological model, providing us with a quantitative picture of how perturbations grew from very low amplitude fluctuations, we can perform the forward modeling of representative pieces of the universe using standard physical processes, to see how well our computer simulations match real, locally observed galaxies. Finally, we can employ large ground and space based telescopes to use the universe as a time machine – directly observing the past history of our light-cone, and comparing with our computed evolutionary tracks. I will present the coherent and plausible picture that emerges and that leads naturally to the mass, size, scale and epoch of galaxy formation.