Many of plants spend their whole life where they grew up. To fit their growth and development for the surrounding environments, plants sense and respond to the direction of gravity and light, the gradients of water and chemicals, and so on. It is very interesting that in plants various environmental cues are recognized by each cell and are integrated to control the behavior at the tissue and individual levels, while animals sense the stimuli by the sensory organs and transmit the information over the nervous system. We have focused to elucidate the mechanism by which plants sense the changes in the environments and respond to them, particularly on the gravity response.