Planet
The smallest known planet is PSR B1257+12A, one of the first extrasolar planets discovered, which was found in 1992 in orbit around a pulsar. Its mass is roughly half that of the planet Mercury. The smallest known planet orbiting a main-sequence star other than the Sun is Kepler-37b, with a mass (and radius) slightly higher than that of the Moon.
Mini-Neptune
A mini-Neptune or sub-Neptune (sometimes known as a gas dwarf or transitional planet) is a planet of up to 10 Earth masses (), less massive than Uranus and Neptune, which have about 14.5 and 17 , respectively. Mini-Neptunes have thick hydrogen–helium atmospheres, probably with deep layers of ice, rock or liquid oceans (made of water, ammonia, a mixture of both, or heavier volatiles).