A millimeter-scale thermophotovoltaic generator was built and characterized. The generator consists of a MEMS microreactor with integrated 1D photonic crystal, four 0.54 eV InGaAsSb cells, and a maximum power point tracker. The microreactor is a 1 cm square of silicon with a serpentine channel etched through it. The channel is loaded with a platinum catalyst that supports combustion of propane in oxygen. A silicon/silicon dioxide stack deposited directly on the microreactor enhances above-bandgap thermal emission and suppresses below-bandgap emission. The maximum power point tracker steps up the voltage from InGaAsSb array to 3.6 volts while providing on-the-fly impedance matching between the cells and the load to ensure the cells are always operating at their maximum power point. With a fuel input of 10 W, the microreactor reaches approximately 800◦C. At this operating point, the system has demonstrated fuel to electricity efficiencies of over 2% and delivers 220 mW to the load. With several simple improvements to the system, efficiencies of 3-4% should be achievable at similar operating conditions.