The Geminids are one of the best meteor showers of the year with numerous (ZHR~120) and bright (r~2) meteors! The parent body is an asteroid named 3200 Phaethon, which is believed to be a candidate for an extinct cometary nucleus, a mystery by itself. Moreover, during the last perihelion passage of the asteroid its magnitude increased unexpectedly (almost doubled), which is thought to be connected to some ejected dust originated from break-down of surface rocks. But this dust can account only for the 0.01% of the total material which is needed to supply the stream in order to see this activity each year this show.
How this object has manage to give out so much material? Geminids are not ready yet to reveal their mysteries…
The source and paper ( by journal or author) / Jewitt D. & Li J., Activity in Geminid parent (3200) Phaethon, AJ, 140, 1519, 2010.