There isn't one specific type of scientist who builds body parts. It's a field that combines expertise from various disciplines:

* Biomedical Engineers: They design and develop artificial organs, prosthetics, and other medical devices.

* Tissue Engineers: They focus on growing and repairing tissues and organs using living cells.

* Material Scientists: They develop new materials for use in medical implants and devices.

* Geneticists: They study and manipulate genes to potentially grow organs or create new cells for repair.

* Surgeons: They perform the procedures to implant and connect artificial or engineered body parts.

So, depending on the specific task of building a body part, the scientist could be any of the above. It's often a collaborative effort between multiple specialists.