Terraforming

The artificial creation of a habitable environment on a planet or other celestial body. Terraforming is a type of megascale engineering, requiring the importation and processing of vast amounts of resources in order to build up an atmosphere, hydrosphere, and biosphere on the target world.
Terraforming engineers will prefer to start with planets already possessing a pre-existing, albeit thin or unbreathable atmosphere and render those habitable before moving on to more difficult prospects like completely airless moons as economic development demands more living space. Each world will generally get its own ecology with life custom-tailored to its the gravitational, atmospheric, and other characteristics.
For the smallest bodies, terraforming is not possible since an atmosphere would quickly escape into space. Instead, the entire world is roofed off with a transparent coating several kilometers above the ground, suspended by numerous tall towers, and filled with air inside in a process known as paraterraforming or worldhousing. This can also be done over part of a larger planet if full terraforming is not feasible or desired for some reason.
Not an easy feat by any stretch of the imagination, terraforming requires an immense investment and the ability to mobilize vast amounts of resources and processing capacity. Therefore, it is unsuited for profit-driven organizations chasing after short-term gain, being more for those who take a longer-term view focused on building towards a better future. Wealthy nations may be able to terraform their own colony planets, while others will often pool their resources into consortium and receive a land-share on the resulting world. In the present day the Stellar Compact has funded the terraforming of planets open to colonization by anyone with the ability to stake a claim.