Liquid phase electron microscopy. Liquid phase or liquid cell transmission electron microscopy (TEM) is a powerful and emergent platform for nanoscale imaging and characterization of physical, chemical, and biological processes of materials in liquids. It can be used to explore nanoscale details of solution processes directly. Details of the development and applications of liquid cell TEM are discussed in this issue of MRS Bulletin. The cover shows a stylized representation of liquid phase TEM. The smaller image in the top left is a microfabricated fl ow liquid cell that sandwiches a thin layer of solution containing either a precursor solution or nanoparticles between two ultrathin SiNx membrane windows that are separated by a spacer. On the bottom left is a static graphene liquid cell that sandwiches nanodroplet pockets of precursor solution between two graphene layers. See the technical theme that begins on p. 704.