Numerous microdevices developed for single-cell analyses have been presented in the last decades. Practical usefulness in biological and clinical settings has become an important focus during the development and implementation of new structures and assays. Single-cell analysis has been applied in intracellular research, gene- and protein content and expression, PCR, cell culture and division, clone formation, differentiation, morphology, lysis, separation, sorting, cytotoxicity and fluorescence screens, antibody secretion, etc. as discussed here along with brief descriptions of the technical devices used for the studies, e.g. well-, trap-, pattern-, and droplet-based structures. This review aims to serve as an overview of available techniques for single-cell analysis by describing the different biological single-cell assays that have been performed to date and how each individual application requires a particular device design.