Today, Mercury is passing between the Earth and the Sun, in an event known as a solar transit. That means that over the course of 7.5 hours, the tiny planet will appear as a small black dot slowly creeping across a portion of the Sun's disc. It may be a slow trot, but Mercury's crossing happens only 13 times a century, so try not to miss it.
If you want to see the transit yourself, you need a telescope, as well as a specialized solar filter. Fortunately, NASA and other observatories are covering the event for those of us without fancy equipment. Astronomers are observing the transit with high-powered telescopes and satellites, providing pictures and live streams for the space geeks out there.
Check back here throughout the day to see some of the photos, and catch a live stream of the event here.