The basic unit of video is the frame (or in interlaced material, the field). There is no smaller unit.
Temporal resolution is dependent on the acquired source frame rate -
shoot at a normal 30 frames per second, each frame displays 1/30th of a second.
You can shoot footage with specialized cameras that shoot, for example, 16,000 frames per second, so each frame will display 1/16000 of a second.