Aether

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

It contains a new liquid called Shimmer, Gem Trees, 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 commonly underneath in the outer 4ths of the World on the same side as the Jungle next to the Ocean about 400 blocks down.