Transmission electron microscopy (TEM) is a powerful tool that has been used for the visualization of biological materials since the 1940s. This technique permits the detailed observation of cellular organelles and other intracellular structures as well as infectious agents, like viruses. Important insights about the structure and function of the cell nucleus have been gleaned using TEM. Here we present a method for visualization of the nuclear envelope in cultured HeLa cells using TEM. The method covers cell culturing, fixation, embedding, sectioning, staining, and visualization. This approach is particularly useful to understand how the ultrastructure of the nuclear envelope is affected by cell culture conditions, genetic manipulations, and stress treatments.