BIOINKS are a mixture of living cells and biomaterials. Usually, the living cells are grown in a cell culture incubator separately, while the special biomaterial formulations (called hydrogels) are mixed with the cells afterwards, often just prior to the bioprinting process, and serve as a scaffold. Thus, the mixtures of cells and the hydrogels form the BIOINKS, to which bioactive molecules, such as growth factors, can also be added. These molecules play various roles, most importantly including the support and guidance of the cell functions into desired pathways. The hydrogels, due to their high water content and the structure of the comprising molecules, are rather jelly-like substances. They can be easily placed into a syringe-based extruder and be extruded from its nozzle.