Researchers whose work focuses on self-assembled structures in the biological sciences or nanostructures in the materials sciences are interested in high-resolution imaging. Certain self-assembled structures occupy a size range where the theoretical limit of resolution by light microscopy (LM), which is on the order of 160 nm, is not adequate to image them. The cell creates several types of protrusions. The filopodium (plural, filopodia) is a slender, tapering extension of cytoplasm with a mean width of 50-100 nm. Filopodia are especially challenging to visualize, because they may broaden to >160 nm at the base where they integrate with the rest of the cytoplasm. Although the broader parts of the structures are often used to estimate the prevalence of filopodia on cells, the greatest number of the structures may be missing from the image viewed by LM. Thus, LM imaging gives inaccurate and misleading results. To accurately assess their prevalence, filopodia must be imaged with a high-resolution instrument or modality. The filopodia serve as only one example of a cell surface structure that is at or beyond the LM limit. Additional features, such as microvilli, coated pits, caveolae, and stereocilia, use self-assembly processes to create structures in the sub-LM range.