Aether

The Aether is a mini-biome introduced in the 1.4.4 Labour Of Love Update

It contains Gem Trees, a new liquid called Shimmer, and spawns Faelings

The Shimmer also contains a unique background making all fully dark blocks appear with stars (It ressembles the background from Space)

It is possible to create a new Aether Biome with enough Shimmer

The Aether biome is found underground in the outer 4ths of the World on the same side as the Jungle next to the Ocean around 400 blocks down.