Brassinosterois (BR) are a group of steroidal plant hormones. Brassinolide was the first of these steroid compounds discovered in 1973, when it was shown that pollen from Brassica napus could promote stem elongation and cell divisions and that the biologically active molecule was a steroid that the authors called Brassins. The yield of Brassinosteriods from 230 kg of Brassica napus pollen was only 10 mg. Since their discovery, over 70 BR compounds have been isolated from plants.