Abstract: The NASA Magnetospheric Multiscale (MMS) mission was launched on March 13, 2015 UT to investigate magnetic reconnection in near-Earth space.  During the first dayside phase ( 1A ), the four MMS spacecraft were deployed in a tetrahedral configuration with separations ranging from 400 km down to 10 km, a scale close to that of electron reconnection diffusion regions. Data is available from very high time resolution 3D plasma measurements (<30 keV, with a cadence of 30 ms and 150 ms for electrons and ions, respectively), 3D magnetic and electric fields (greater than with 1 ms time resolution)  and waves (<6 kHz), 3D energetic particles with composition up to 500 keV, and plasma ion composition (< 30 keV/q). This talk with review the results of the first dayside encounters with electron diffusion regions and the acceleration observed during these encounters, where the dissipation during reconnection appears to be significant.