There are many types of clouds in the sky. Cirrus, cirrostratus, and cirrocumulus clouds are considered high clouds, which are 16,500-45,000 feet high. Altocumulus, altostratus, and nimbostratus clouds are all mid-level clouds, which are 6,500-23,000 feet high. Lastly, there are low clouds that are less than 6,500 feet high, and these consist of cumulus, stratus, and cumulonimbus clouds.
There are two types of clouds that I found especially intriguing: mammatus clouds and orographic clouds. Mammatus clouds have pouch-like hangings on the bottom of them. These pouches form when the cold air inside of the cloud starts to move and sink towards Earth. If these clouds are in the sky, it is possible that severe weather is on its way. Orographic clouds can be shaped by mountains, hills, or sea breezes. They form over or around hills and mountains. When these clouds are in the sky early, it is possible that there will be afternoon thunderstorms.
Something that I find especially interesting is the conspiracy theory of chemtrails. Supposedly, they are clouds of chemicals in the sky designed by the government for wicked and evil purposes. Believers of this conspiracy are convinced that these chemicals are used to modify the weather, control the human population with sterilization, and for mind control purposes. They are known to be the white clouds that planes leave behind. The natural clouds that planes leave behind them should disappear quickly, so any cloud behind a plane that does not disappear immediately is said to have these dangerous chemicals in there. I find this conspiracy really creepy.
Something else I find fascinating is cloud iridescence, or irisation. Irisations get their name from the Greek goddess Iris: the goddess of rainbows. This is a colorful optical phenomenon occurring in clouds that are close to the Sun or the Moon. This is considered a type of photometeor. This is fairly common and occurs in altocumulus, cirrocumulus, lenticular, and cirrus clouds. The iridescence is caused by small water droplets or ice crystals scattering light.