Upon being generated, each world has one or more broken machines hidden somewhere in the depths of the earth. The parts to fix the machine are in large green crates scattered among dungeons that are usually heavily guarded by hostile mobs. Clicking on a green crate amounts to the discovery of one machine part. When all the parts are found, the machine must be activated. Different biomes have different types of machines, and once activated, each machine gives a different kind of benefit.
Finding a machine part will count towards the ecologist achievement.