In the latest study by Prof. Dr. Leonid Ionov, Professor of Biofabrication, and his team at the University of Bayreuth, various types of hydrogels were extensively tested for the 3D printing of tissues. A hydrogel is a water-retaining and also water-insoluble polymer. In addition, the cell containing–hydrogels, also known as bioink, are combined with fibers to create a composite material.