Structured illumination microscopy (SIM) is a super-resolution uorescence microscopy technique that can provide both increased resolution, beyond the diraction limit of light, and excellent optical sectioning. Several commercial super-resolution SIM systems are available, and are accessible to users at many academic imaging facilities: DeltaVision OMX (by GE/Applied Precision), ELYRA (by Zeiss), and N-SIM (by Nikon). ese systems provide many of the advantages of the traditional, wideeld, light microscope. Fluorescently labeled xed or living biological specimens can be imaged with visible light, mounted on a microscope slide under a coverslip or in a glass-bottom cell culture dish. In terms of light dose, SIM is mild on the sample compared to other superresolution techniques. Standard, linear SIM achieves a factor of two resolution improvement, producing images with around ~100  nm lateral and ~300  nm axial resolution. Even ner details can be resolved when linear SIM is combined with TIRF. Using a nonlinear SIM approach, true super-resolution imaging with theoretically unlimited resolution is possible. ere is no hard limit to what resolution can be obtained, but the signal-to-noise ratio (SNR) of the data in practice determines what resolution can be reached (Heintzmann et al. 2002, Gustafsson 2005). e highest resolution nonlinear SIM data reported in biological imaging to this date is ~50 nm (Rego et al. 2012).