A capsule device with density control is disclosed, where the density of the capsule device is set to desired specific gravities when it travels to designated regions of the gastrointestinal track. The density control means will cause at least two specific gravities of the capsule device for at least two designated regions of the gastrointestinal track respectively, wherein each of said at least two specific gravities is selected from a first group consisting of a greater-than-one state and a less-than-one state. In one embodiment, the greater-than-one state correspond to the specific gravity of about 1.1 or larger and the less-than-one state corresponds to the specific gravity of about 0.94 or smaller.