Stages of 3D-bioprinting, illustration. Three-dimensional (3D) bioprinting allows artificial construction of viable tissues and organs such as heart, kidney, liver and others, for research or with the aim of transplantation. Several techniques are used, the most common are drop-based bioprinting (inkjet) and extrusion bioprinting. MRI and CT scans and software are used to generate a model of an organ or tissue. Stem cells or other cells are combined with growth factors, nutrients and appropriate matrix material to form bioink. Bioinks can be deposited in precise layers interspersed with a gel that forms a temporary mould around the cells. The gel is removed leaving the printed tissue. Scaffold structures for organs and tissues can also be generated using 3D bioprinting.