We are all familiar with rainbow and how it is formed. But, have you ever seen a rainbow within clouds? This phenomenon is called cloud iridescence. It is a Greek personification of the rainbow does Cloud Iridescence form?
Cloud iridescence is a diffraction phenomenon caused by small water droplets or small ice crystals individually scattering light. Iridescence is therefore mostly seen at cloud edges or in semi-transparent clouds, while newly forming clouds produce the brightest and most colorful iridescence.
And for you to observe this phenomenon, you need to place the sun itself behind foreground object, a building or a mountain.Other aids are dark glasses, or observing the sky reflected in a convex mirror or in the pool of water.