Nacreous clouds, also known as mother-of-pearl clouds, are rare, colorful clouds that form in the stratosphere, typically at altitudes of 15 to 25 kilometers. They appear during winter months in polar regions and are best observed during dawn or dusk when sunlight illuminates them, creating a shimmering effect. These clouds are composed of tiny ice crystals and can display a range of colors, including pink, blue, and green. These clouds are often associated with polar stratospheric clouds, which play a role in ozone depletion. Nacreous clouds form when water vapor freezes at very low temperatures, leading to their unique appearance. While they are beautiful, their presence can indicate specific atmospheric conditions that may affect the environment.