If during the day the ground is heated by the sun and in the evening again is cooled, then is cooled and the air above its surface. Invisible particles of water are condensed in this air, and water droplets accumulate on the grass, the trees, the stones. This occurs most often in summer and autumn nights. Early in the morning you can see how sparkling drops of dew, lit by the rays of dawn. As soon as the air is warmer, the dew evaporates.