Mother-of-pearl clouds, also known as nacreous clouds, are a rare type of cloud that form in the stratosphere, typically at altitudes of 15 to 25 kilometers. They are most commonly observed in polar regions during winter months. These clouds are composed of tiny ice crystals that refract sunlight, creating a shimmering, iridescent appearance. The colors of mother-of-pearl clouds can range from soft pinks and blues to vibrant greens and purples, depending on the angle of the sun and the observer's position. Their beauty is often fleeting, as they can dissipate quickly with changing weather conditions.