Here is a movie of the transit (from our flight dynamics team.)
Mercury is smaller and further from the Earth, so, compared to the transit of Venus in 2012, it will be a smaller disk as it passes between SDO and the Sun. Due to its shorter orbital period, transits of Mercury are more common than transits of Venus.
Johannes Kepler predicted a transit of Mercury would occur in November 1631. The first observed transit of Mercury was on November 7, 1631 by Pierre Gassendi. This was the first observed planet transit and showed that Kepler's equations of planetary motion could be used to accurately predict the positions of planets.
From the ground the transit starts at 1235 UTC (7:35 am ET, first contact) and ends at 1804 UTC (1:04 pm ET, fourth contact. Parts of this transit will be visible throughout North America. People in the eastern USA will be able to see most, if not all, of this transit. People in the western USA will see the Sun rise with Mercury already on the disk.
SDO will provide near-realtime pictures of the Mercury Transit at https://mercurytransit.gsfc.nasa.gov/2019/.