This book provides a molecular view of membrane transport by means of numerous biochemical and biophysical techniques. The rapidly growing numbers of atomic structures of transporters in different conformations and the constant progress in bioinformatics have recently added deeper insights. The unifying mechanism of energized solute transport across membranes is assumed to consist of the conformational cycling of a carrier protein to provide access to substrate binding sites from either side of a cellular membrane. Due to the central role of active membrane transport there is considerable interest in deciphering the principles of one of the most fundamental processes in nature: the alternating access mechanism. This book brings together particularly significant structure-function studies on a variety of carrier systems from different transporter families: Glutamate symporters, LeuT-like fold transporters, MFS transporters and SMR (RND) exporters, as well as ABC-type importers. The selected examples impressively demonstrate how the combination of functional analysis, crystallography, investigation of dynamics and computational studies has made it possible to create a conclusive picture or more precisely, a molecular movie . Although we are still far from a complete molecular description of the alternating access mechanism, remarkable progress has been made from static snapshots towards membrane transport dynamics.