We demonstrate complete integration of a fluorescence-based assay in that the analyte well is also an optical emitter. Laser machining is used to create 'active micro-wells' within semiconductor light emitting diode and laser structures. These are then used to optically excite fluorescently-labelled beads in solution within the well. The results show efficient illumination on a par with traditional lamp-based excitation. This technology therefore provides active micro-well plates with completely localized excitation, confined to the analysis well, that can be engineered via the micro-well geometry. The micro-wells have also been machined within the cavity of lasing semiconductor structures and coherent emission maintained. Thus lasing multi-well plates are also realizable.