Microbubbles and nanobubbles have several characteristics that are comparable with millimeter- and centimeter-sized bubbles. These characteristics are their small size, which results in large surface area and high bioactivity, low rising velocity, decreased friction drag, high internal pressure, large gas dissolution capacity, negatively charged surface, and ability to be crushed and form free radicals. Microbubbles and nanobubbles have found applications in a variety of fields such as engineering, agriculture, environment, food, and medicine. Microbubbles have been successfully used in aquacultures of oysters in Hiroshima, scallops in Hokkaido, and pearls in Mie Prefecture, Japan. This field has shown a strong potential for growth. This book comprehensively discusses microbubbles and nanobubbles and their application in aquaculture, environment, engineering, medicine, stock raising, agriculture, and marine industry. It presents their potential as a new technology that can be utilized globally.