The majority of clouds can be classified into three main groups based on how high or low they sit in the sky. However, some, like Lenticular clouds, are grouped by other characteristics such as the location where they form.
High-level clouds include cirrus and cirrocumulus.
Mid-level clouds include altocumulus and altostratus.
Lower-level clouds include stratus and nimbostratus.
The composition of clouds is dependent upon their altitudes. High-level clouds (ones forming above 20,000 feet) are mainly composed of crystalized ice, according to the University of Illinois. Whereas clouds forming between 6,500 to 20,000 feet primarily contain a combination of water droplets and ice. Lower-level clouds forming below 6,500 feet are generally composed of water droplets and snow when the temperature drops.
Click through the gallery to see what the different types of clouds look like.