Microcompartmentation refers to nonhomogeneous distribution of solutes in compartments of cells or associated structures without intervening membranal barriers. Such variations in concentration of ions, metabolites, intracellular messengers, and nutrients can introduce significant heterogeneity in subcellular function and regulation. The current focus on biological examples of microcompartmentation provides ample evidence for its importance and the role of physical structure in determining local chemical environments. The examples present in the different chapters include...