Neptune is an ice giant, which is a type of gas giant, as opposed to a terrestrial, or rocky, planet. Neptune is the eighth planet from the sun and the fourth largest. It is made of layers although they aren't very distinct. The composition of the layers is shown in the diagram.
Neptune appears blue because red light is absorbed by traces of methane in its atmosphere. The atmosphere is icy and is composed mostly of hydrogen and helium. It has active weather systems and is one of the coldest regions of our solar system. There is a hot dense liquid mantle region below the atmosphere. It consists of ammonia, water and methane. Neptune's core is made of iron, nickel and ice. It has faint rings that were visible in Voyager 2 images. It has 14 known moons.