The emission mechanism for Type I bursts is generally agreed to be fundamental plasma emission due to the high circular polarization fractions that are frequently observed. However, there is no consensus yet on what process accelerates the electrons needed to stimulate plasma emission. The leading ideas are minor magnetic reconnection events or shock waves driven by upward-propagating waves. Since the year 2000, different magnetic reconnection scenarios have generally been favored. One scenario involves reconnection between the open and closed magnetic fields at the boundaries of active regions, and another involves moving magnetic features in the photosphere.