The invention concerns a process for producing a three-dimensional bioartificial tissue having viable cells in or on a matrix, and by which cells and matrix can be cultivated into a tissue or a precursor of a tissue, a vascularized tissue of biological materials, obtained by this process, and an experimental reactor for scientific purposes and for producing clinically usable tissues and organs. These legacy blocks leave at least one corner of the device unoccupied by such legacy circuitry. A plurality of distally projecting rods is mounted on the buoyant reef bodies.