Its name derives from Greek and literally means "cavity", referring to the hollow shape of its fleshy leaves. These are semi-shrubby plants, which can take on very different forms, generally characterized by long stems which, with growth, tend to branch off, taking on the appearance of a thick continuous bush. It has leaves that store water, which are rounded or sometimes oval, whose shades vary between green and blue, even whitish in some species. Such species have a dusty coating that helps the plant to protect the leaves and not make it lose liquids. In others species the leaves take on showy reddish shades. Due to the shape of its foliage it is also commonly known as "pig's ears". It is a perfect genus for any environment, it is very easy to grow, is extremely decorative, perfect even for beginners or for those who want to give a touch of green when having little time available!