Clouds
Water is a shape shifter: familiar in its liquid and frozen forms, it is invisible in its third form, as a vapor, until it coalesces into clouds overhead or shrouds us in ghostly fog. One of nature's everyday wonders, clouds hide in plain sight until they are touched with the sun's glory at sunrise and sunset or pile up to form a lightning-generating, anvil-headed cumulonimbus thundercloud.

• The Book, "TIME Planet Earth: An Illustrated History"