This is one of my favorite Cassini images.
A brief explanation from Wikipedia:
On July 19, 2013, in an event celebrated the world over, NASA's Cassini spacecraft slipped into Saturn's shadow and turned to image the planet, seven of its moons, its inner rings -- and, in the background, our home planet, Earth. This mosaic is special as it marks the third time our home planet was imaged from the outer solar system; the second time it was imaged by Cassini from Saturn's orbit; and the first time ever that inhabitants of Earth were made aware in advance that their photo would be taken from such a great distance.
In the lower right of the mosaic, in between the bright blue E ring and the faint but defined G ring, is the pale blue dot of our planet, Earth.
You can enlarge it enough to play around with it and see the tiny dots of the planets. Though I admit I find it difficult to work out whether I've seen a planet or been confused by a star.
This helps to locate Earth on the other photos.
