About 1600 species with a large range of leaf shapes, sizes, textures and colours and many,
particularly hybrids, are cultivated as ornamentals.
Most are compact plants under 30 cm high, often epiphytic.
Most have thick, succulent stems sometimes coloured pink or red.
Leaf arrangement is usually alternate but can be opposite or whorled.
They usually have petioles (sometimes attached to the centre of the blade) but have no stipules.
Leaves are usually fleshy and most are round, others are heart-shaped, oval or lanceolate.
Leaves are green but can be striped, marbled or variegated.
The edge may be yellow, cream, red or a paler green.
The surface can be smooth, wrinkled or furrowed.
Yellow-green or brown inflorescences, on stalks, are spikes with tiny densely packed flowers.
Each flower has a small bract but lacks a perianth.
There are 2 stamens that open outwards via longitudinal slits.
There is 1 carpel with 1 stigma and a single ovule.
The fruit is a drupe.