A system for forming a three dimensional tissue element within a subject, said system comprising: a cannula configured for insertion into said subject through a surface opening having lateral dimensions substantially similar to those of said cannula, the proximal end of said cannula being configured to be attached to a surgical robot and the distal end comprising a nozzle adapted to eject one or more bio-inks to form at least one layer of biomaterial within said subject; at least one bio-ink extruding mechanism configured to eject said one or more bio-inks from the distal end of said cannula; and a controller adapted: (i) to direct said surgical robot to adjust the longitudinal position and the orientation of said cannula within said subject in accordance with a preoperative surgical plan based on at least a three-dimensional preoperative image set; and (ii) to control said extruding mechanism such that said bio-ink is ejected in accordance with said longitudinal position and said orientation of said cannula within said subj ect, characterized in that said surgical robot is configured to perform said adjustments of said orientation of said cannula within said subject, using said surface opening as a pivot point for said orientation of said cannula, so that a three-dimensional tissue element having dimensions larger than the lateral dimensions of said cannula can be formed within the subject; and wherein said cannula is configured to house at least two bio-inks in layers arranged sequentially along the length of said cannula, said layers having predetermined amounts, compositions, and order. a cannula configured for insertion into said subject through a surface opening having lateral dimensions substantially similar to those of said cannula, the proximal end of said cannula being configured to be attached to a surgical robot and the distal end comprising a nozzle adapted to eject one or more bio-inks to form at least one layer of biomaterial within said subject; at least one bio-ink extruding mechanism configured to eject said one or more bio-inks from the distal end of said cannula; and a controller adapted: (i) to direct said surgical robot to adjust the longitudinal position and the orientation of said cannula within said subject in accordance with a preoperative surgical plan based on at least a three-dimensional preoperative image set; and (ii) to control said extruding mechanism such that said bio-ink is ejected in accordance with said longitudinal position and said orientation of said cannula within said subj ect, (i) to direct said surgical robot to adjust the longitudinal position and the orientation of said cannula within said subject in accordance with a preoperative surgical plan based on at least a three-dimensional preoperative image set; and (ii) to control said extruding mechanism such that said bio-ink is ejected in accordance with said longitudinal position and said orientation of said cannula within said subj ect, characterized in that said surgical robot is configured to perform said adjustments of said orientation of said cannula within said subject, using said surface opening as a pivot point for said orientation of said cannula, so that a three-dimensional tissue element having dimensions larger than the lateral dimensions of said cannula can be formed within the subject; and wherein said cannula is configured to house at least two bio-inks in layers arranged sequentially along the length of said cannula, said layers having predetermined amounts, compositions, and order.