Kitty has the ability to pass through solid matter by passing her atoms through the spaces between the atoms of the object through which she is moving. In this way she and the object through which she is passing can temporarily merge without interacting, and each is unharmed when Shadowcat has finished passing through the object. This process is called phasing, and it renders her almost completely intangible to physical touch. Shadowcat passes through objects at the same rate of speed at which she is moving before she "enters" them. Since she is unable to breathe while "inside" an object, she can only continuously phase through solid objects (as when she travels underground) as long as she can hold her breath.