One day a Zen-Master is walking to a temple on top of a mountain and there are a lot of steps till the top of the mountain where the temple is. His student is following him and they both climb the stairs very quietly and calmly. The student asks the master "Master. Tell me what is Zen?" and the master climbs the stairs quietly for a moment and points at the feet of the student and says "mind your step" and keeps on climbing the stairs quietly.