This era of ongoing discovery has shown us a "new" solar system, one brimming with unanticipated beauty, diversity, and mystery. Our robotic emissaries have visited every planet except Pluto. Through these explorations we have mapped the faces of our distant neighbors, dug into their soils, and plumbed their exotic atmospheres. And astronomers now realize that ours is but one of many solar systems in our part of the Milky Way galaxy. This book summarizes the fruits of our interplanetary explorations over the last quarter century.