1. A three-dimensional bioprinter comprising: a. one or more printer heads, wherein a printer head comprises a means for receiving and holding at least one cartridge, wherein a cartridge comprises at least one deposition orifice and contents comprising a bio-ink, wherein the bio-ink comprises solid or semi-solid aggregates of living cells; b. a means for calibrating a position in space of the at least one cartridge or the at least one deposition orifice utilizing a laser and a laser detector; c. a means for extruding the contents of the at least one cartridge by application of pressure, utilizing a piston; d. a receiving surface for receiving the extruded contents of the at least one cartridge; and e. a programmable computer processor communicatively connected to the means for calibrating and the means for extruding, the programmable computer processor for positioning the one or more printer heads in three dimensions and regulating the extrusion of the contents of the at least one cartridge.