Introduction.- Evolution of type III secretion systems.- Transcriptional and post-transcriptional regulatory mechanisms controlling type III secretion.- Assembly of type III secretion machines.- Structure of the type III secretion needle complex.- Structure and assembly of filamentous structures associated with type III secretion machines.- Structure and function of the type III secretion-associated sorting platform.- Molecular organization and assembly of the protein export apparatus.- Export mechanisms and energy transduction in type III secretion machines.- Needle length control and substrate switching in type III secretion machines.- The tip complex: sensing the host cell.- Chaperones and targeting mechanisms.