The demand for natural food colourants is increasing because of public awareness of their health benefits. Betalains are nitrogen-containing plant pigments whose colours range from red-violet betacyanins to yellow betaxanthins. They are used for colouring dairy products, meat and frozen desserts. Betalains have attracted additional interest because of their antioxidative, anti-inflammatory and anticarcinogenic properties. The main source of commercially produced betalains is red beet root, but alternative sources are found in plants from the Amaranthaceae and Cactaceae families. Another alternative source is plant cell culture in bioreactors, although optimization of pigment production seems necessary. In this paper we synthesize the results of recent studies on betalain biosynthesis, chemical properties, sources, biotechnology and applications.