Various superimposing beam controls that can superimpose beams of light with different optical properties are described. In one aspect, a beam control receives a beam of light and outputs one or more beams. Each beam is output in a different polarization state and with different optical properties. Superimposing beam controls can be incorporated in fluorescence microscopy instruments to split a beam of excitation light into one or more beams of excitation light. Each beam of excitation light has a different polarization and is output with different optical properties so that each excitation beam can be used to execute a different microscopy technique.