Abstract: The present invention discloses a portable, collapsible, and width-adjustable dolly and track system for movably supporting a cameraman and a tripod with a camera mounted thereon. The track system comprises a plurality of track sections, straight or curved, interconnected together to form either a straight track or a curved track. Each track section comprises a pair of parallel rails and two connecting members pivotally connecting the parallel rails. The track sections are pivotally operable for adjusting their width. The first embodiment of the dolly mainly includes two bars detachably connected in a T-shaped configuration. The second embodiment of the dolly mainly includes a plurality of inner and outer arms detachably connected together. The two embodiments of the dollies include a plurality of mounting points, wherein any of them are selectable to detachably assemble the dolly for achieving different widths.