The pressure cooker seals the water quite closely. The water vapor generated by water evaporation cannot diffuse to the air, but can only be retained in the pressure cooker, which makes the pressure inside the pressure cooker higher than 1 atmosphere, and also makes the water boil when it is higher than 100 ℃. In this way, a high-temperature and high-pressure environment is formed inside the pressure cooker, and the rice is easy to cook quickly, and it is quite crisp. Of course, the pressure in the autoclave will not be unlimited, or it will explode.