We know that a single spring and mass system obeys simple harmonic motion (SHM). But how does a system of two spring and mass oscillators, coupled by a third spring behave? The analysis of this system of coupled oscillators is a great introduction to the concept of normal coordinates, and normal modes of vibration. For the normal modes of vibration, the motion is SHM. However, the general behavior of the two mass system is not SHM. It is a much more interesting motion in which the energy of the system oscillates back and forth between the two masses. The analysis here shows the general solution for the two mass system, in the undamped, undriven case.