Abstract
Membrane contact sites (MCSs) are microdomains that exchange ions and lipids between the membranes of two organelles. They facilitate the exchange of metabolites and act as a site for intracellular communication through material transport. Because of the important physiological significance of MCSs in localizing the exchange of substances and metabolic regulation, they are considered to play an important role in cell biology. Understanding MCS structure is essential for analyzing how substances move to and from each organelle. Several methods have been developed to analyze MCS function, with electron microscopy (EM) being the predominant technique when structural detail is needed. In this review, we summarize the ultrastructure of MCSs and how EM can be used to determine their role in cell biology.