An illumination system for a fluorescence microscope is provided. The illumination system includes a carriage removably receivable within the microscope and a plurality of filter cubes movably arranged on the carriage, wherein each filter cube is moveable between an active position and an inactive position. Each filter cube includes a housing having first and second openings and a solid state light source secured to the housing. The solid state light source emits light when the filter cube is moved into the active position. Each filter cube further comprises at least one optical filter disposed within the housing, wherein the optical filter corresponds to the solid state light source.