Thermal (or boiling) bubbles have been successfully applied in ink-jet printers and microbubble-powered actuators. Technologies still in the research and development stage for possible applications include micropumping in microchannels, fluid mixers for chemical analysis, fuel mixers in combustion, prime movers in micro steam engines, and cooling of semiconductor chips in electronic devices. Observation of boiling phenomena on microstructures requires use of microscope. On the other hands, bubbles depart from a micro heater with macro-scale sizes. This odd coupling of micro and macro events suggests possible distinctions in mechanisms and concepts between the conventional (macro-scale) and micro-scale liquid-to-vapor phase changes, due to enormous differences in heat transfer surface sizes. This article summarizes progress to date in boiling phenomena, particularly of characteristics of microbubbles on microstructures. What we need to know to develop high-tech applications of micro boiling phenomena is discussed.