Cells and organelles are small units for biochemical synthetic purposes, often the smallest practically feasible unit since they contain coenzyme regenerating system, ordered enzyme sequences, etc.These volumes, besides giving some insight into basic technology (immobilisation procedures, etc.), also sum up the current know-how in this subject area and try to predict some future trends.The termimmobilized cells covers everything from dead cells with a single active enzyme species to cells proliferating on or within a three dimensional polymer matrix. The practical handling of these structures make them useful in various applications, e.g. large-scale production of biomolecules, biodegration, analysis, etc.