Abstract: A bio-artificial organ system is provided comprising a wall surrounding a space which has a solid support for cell cultivation. The space includes a there dimensional matrix in the form of a highly porous sheet or mat and including a physiologically acceptable network of fibers or an open-pore foam structure; hydrophobic hollow fibers permeable to gaseous oxygen or gaseous carbon dioxide evenly distributed through the three dimensional matrix material and arranged in parallel running from one end of the matrix material to the other end of the matrix material. Cells obtained from organs are present in the extra fiber space for culture wherein the cells are provided with sufficient oxygenation and are maintained as small aggregates with three dimensional attachment.