The term "nanofluid" is used to describe a liquid that contains dispersed nanoparticles, which can have unique effects on the liquid, because of the enormous surface area of the nanoparticles and their interfacial force-induced microstructures. The enhanced heat-transfer properties of such nanofluids have been extensively reported in the literature; however, little is known regarding the effects of nanofluids on bubble behavior. Such effects are examined experimentally in this study using hydrophilic nanoparticles with bubble flows in bubble columns and microchannels. The data reveal a significant increase in the gas holdup in bubble columns and a decrease in bubble sizes, signifying an intriguing bubble-nanofluid interactive behavior.