The essence of the Mössbauer effect is not y-ray emission without recoil, but it is y-ray emission without transferring any nuclear transition energy to the internal energy of the crystalline solid. The problem has been first treated classically by starting with the kinematics of y-ray emmission for an idealized nucleus-plus-lattice system. Next, using the basic ideas of quantum mechanics, it has shown that the effect is a guantum mechanical phenomenon and can not be explained classically.