Both cloud and fog are composed of the suspension of water droplets or ice crystal in the air. Cloud can be imaged as fog in the sky and fog as cloud near the surface of ground or water. There is no essential difference throughout their properties. The only difference is that the water vapor of fog reached saturation near the surface and formed visible minute water droplets. Fog may gradually be evaporated by the sunlight and generally lifted up to form grayish stratiform cloud.