Uranus discovered accidentally by WIlliam Herschel, 1781. Neptune discovered independently by Urbain Leverrier and John Couch Adams in 1846, using predictions based on Newtonian gravitation and observations of irregularities in the orbit of Uranus that could not be explained by the perturbing effects of the known planets.
Orbits lie close to the plane of the ecliptic.
Long periods mean that Uranus has only been tracked through 3 orbits since discovery, and Neptune through less than one. Masses 20 to 300 x mass of earth. Low densities despite large size, close to that of water. Gassy balls streaked with bands of clouds. Most pronounced on Jupiter, less so on Saturn and Neptune, least on Uranus.