Caveolae are submicroscopic, plasma membrane pits that are abundant in many 
mammalian cell types. The past few years have seen a quantum leap in our 
understanding of the formation, dynamics and functions of these enigmatic 
structures. Caveolae have now emerged as vital plasma membrane sensors that can 
respond to plasma membrane stresses and remodel the extracellular environment. 
Caveolae at the plasma membrane can be removed by endocytosis to regulate their 
surface density or can be disassembled and their structural components degraded. 
Coat proteins, called cavins, work together with caveolins to regulate the 
formation of caveolae but also have the potential to dynamically transmit 
signals that originate in caveolae to various cellular destinations. The 
importance of caveolae as protective elements in the plasma membrane, and as 
membrane organizers and sensors, is highlighted by links between caveolae 
dysfunction and human diseases, including muscular dystrophies and cancer.