Photo Credit: 500px.com/Craig

There are all types of fascinating clouds, and no matter what kind, as they float through the sky they always seem to be making interesting shapes that can provide hours of entertainment just watching them from below.

But some clouds are a lot more rare than others, like mammatus clouds. Their name is somewhat unique too, given that it comes from the Latin word for “breast” or “udder,” making them basically “boob clouds.”

They look like cotton balls or bubbles. The pouch-like protrusions hang from the undersides of clouds, generally thunderstorm anvil clouds, but other types of clouds as well. Composed primarily of ice, they can extend hundreds of miles in any direction, remaining visible in the sky for 10 to 15 minutes at a time.

People associate them with severe weather, and it is that true they can appear around, before or after a storm. But, contrary to a popular myth, they don’t continue extending downward to form tornadoes, but they are interesting in part because they’re formed by sinking air.

Photo Credit: Josh Blash

Mammatus clouds can look smooth, jagged, translucent or opaque depending on atmospheric conditions.

Photo Credit: Flickr: Lorrie McClanahan

The mammatus clouds pictured below were taken by Pam Rice Phillips on May 20, 2013, the day a tornado struck Moore, Oklahoma.

Photo Credit: Pam Rice Phillips

Nature takes many strange and beautiful forms.