Artificial biomes are player-constructed biomes that will spawn the monsters and provide access to most of the other materials that this biome provides. Only certain biomes can be artificially constructed. These are useful for building gardens or otherwise farming for certain items. This guide will explain how to build such biomes.
Some biomes can be constructed within virtually any Layer, at any depth, while others have specific depth requirements. With the exception of the Meteorite biome, no biome will override the Underworld. Any biomes not mentioned below cannot be constructed artificially.
A Forest biome (also called "the Purity" in-game) is the default biome for the Surface layer. When none of the other conditions for a biome are currently fulfilled on the surface, then it is a forest biome.
A Desert biome is defined by the presence of sufficient Sand blocks, in any Layer except the Underworld. Even a single block of sand can spawn desert enemies, as well as grow Cactus and Waterleaf. Deserts can be within any layer. It requires over 1000 blocks of sand to change the background into the desert background, and the presence of sufficient other biome-defining blocks on-screen will override this background.
A flat strip of sand, one block in height, is sufficient to be considered an artificial desert biome suitable for harvesting various Desert materials.
 Surface jungle
The Surface Jungle biome is defined by the presence of Jungle Grass on Mud blocks, but only on the Surface layer. Jungle Grass will cause the spawning of surface jungle enemies, regardless of how many tiles are present. 80 blocks of Jungle Grass, including plants that grow in the tiles above Jungle Grass, are needed to change the background and music into the Jungle biome's natural music and background.
If you have excess mud blocks, it's possible to build a part of skybridge out of mud blocks and plant jungle grass there. Since the trees will grow naturally there, it provides a lot of wood (and fallen stars as well) without the need to navigate through the hilly jungle terrain.
 Underground jungle
|Map Size||Min Start Depth||Average Start Depth||Max Start Depth|
|Small||60 ft||240 ft||420 ft|
|Medium||90 ft||360 ft||630 ft|
|Large||120 ft||480 ft||840 ft|
You can tell the difference between Jungle in the underground and true Underground Jungle by what monsters spawn and whether Jungle Spores grow naturally. If Hornets are spawning or Jungle Spores are visible, then it is a true Underground Jungle.
A Snow biome is defined by the presence of 250 or more Snow Blocks, Ice Blocks (NOT including pink, purple, and red variants) or Snow Bricks. This will change the background and music into the Snow biome's background and music. Below the cavern layer, Underground Snow will be created instead.
Some Snow biome enemies require the presence of Ice Blocks to spawn, while others will appear along with the biome background and music, with particular enemies depending on depth and whether it's raining/snowing or not.
An Ocean biome is defined by all of the following conditions:
- The floor must be made of Sand at least one block thick. Pearl/Ebonsand does not count.
- There must be 7 or more blocks of water above the sand.
- This must be positioned within 250 blocks of either edge of the map.
- This must be above a depth of 0, so within the Surface or Space layers.
This environment will grow Corals and spawn Ocean monsters.
 Hallow, Corruption, and Crimson
The Hallow and Corruption biomes are defined by the presence of their respective hallowed and corrupted blocks, in any layer other than the Underworld. At least 100 Hallowed Grass, Pink Ice Block, Pearlstone, and Pearlsand defines the Hallow; tiles with hallowed plants (including 2-tile tall plants, but not trees) growing on top of hallowed grass also count. At least 200 Corrupt Grass, Purple Ice Block, Ebonstone, and Ebonsand defines the Corruption, with each tile of Vile Mushroom, Thorny Bush and other corrupted plants growing on top of grass counting. At least 200 Crimson Grass, Red Ice Block, Crimstone, and Crimsand defines the Crimson. Note that for purposes of defining a biome, each block of Crimson or Corruption will subtract 1 from the total count of Hallow blocks and vice versa.
The presence of 50 meteorite ore on the screen will transform any environment into a Meteorite biome. All naturally-occurring enemy spawns will be replaced with Meteor Heads, unless this is done in the ocean biome. This works even in the Underworld.
A Mushroom biome is defined by the presence of Mushroom grass, at least one exposed block of which will spawn Mushroom biome enemies if above the surface level of the world. At any depth, this grass will also sprout 1-block-tall Glowing Mushrooms and multi-block Giant glowing mushrooms. At least 100 tiles of mushrooms or mushroom grass are needed to start seeing changes to the music and background, although changing the water color in the biome may take more.
The Dungeon must be below the surface level of the world, and consist of at least 250 blocks of Dungeon Brick. Each tile must also be in front of a naturally-placed Dungeon Wall -- if the player removes and replaces the wall at the same location or elsewhere, it will no longer count towards the requirement, making it impossible to create artificial Dungeon biomes elsewhere.
 Spider Nest
A Spider Nest mini-biome is based on the presence of the special mottled grey/brown cave wall in these areas. Blocks in front of these walls will accumulate Cobwebs up to three tiles deep, and Wall Creepers (pre-Hardmode) and Black Recluses (in Hardmode) will spawn. It's not possible to move or collect this cave wall, so artificial biomes can't be created elsewhere, but a player could set up blocks in an existing nest to affect spawning / allow collection of cobwebs.
The Underworld is defined as roughly the bottom 200 blocks of any world; at around this level, the music and background changes, Underworld enemies will spawn, and water will generally evaporate. An artificial Underworld cannot be created at any other depth.