Starting at 7:35 a.m. ET, it will take more than five hours for Mercury to pass from one side of the sun to the other. That means watchers on the East Coast will be able to see the whole thing, but viewers almost anywhere in North America won't miss out, since Mercury will still be making its journey when the sun is up on the West Coast.
But, just like during an eclipse, viewers will need a solar filter since looking directly at the sun can cause permanent eye damage.
Mercury, the smallest planet in our solar system, will be just a tiny dot on the sun, so NASA recommends using a telescope with a certified solar filter.