Located in downtown Three Cloud City, the HART Building is where the hearts of recently deceased organisms are transplanted into newly constructed robots in order to give them life. The transplant is done in a double blind process that is entirely randomized and secret to all to ensure that no one knows whose heart is powering which robot.
The heart of a recently deceased is placed inside a robot to provide them with an internal source of power. This source of power has the side effect of adding randomness into way that the robots process and run. This randomness is what gave way to sentience.
Although the robots have the heart of another being inside them, they do not necessarily bear resemblance to the donor.
Hearts of organisms are collected by Bluehearts and then dropped off in a receptacle. From here, a complex system of chutes and conveyor belts shuffles the submission and categorizes the heart according to type of being. Hearts are then stored until a completed but empty robot is brought to the factory, at which point the heart is installed.