Brassinosteroids (BRs) are a group of polyhydroxylated plant steroid hormones crucial for many aspects of plant life. BRs were originally characterized for their function in cell elongation, but it is becoming clear that they play major roles in plant growth, development and responses to several stresses such as temperature and drought. A BR signaling pathway from cell surface receptors to central transcription factors has been well characterized. Here we summarize recent progress towards understanding the BR pathway including BR perception and the molecular mechanisms of BR signaling. Next, we discuss the roles of BRs in development and stress responses. Finally, we show how knowledge of the BR pathway is being applied to manipulate the growth and stress responses in crops. These studies highlight the complex regulation of BR signaling, multiple points of crosstalk between BRs and other hormones or stress responses, and finely tuned spatiotemporal regulation of BR signaling.