Map L-systems with dynamic interpretation have been successfully applied to the modeling of the development of two-dimensional cell layers [3, 4]. We extend this technique to three-dimensional cellular structures. The seminal notion of three-dimensional cyclic edge-label-controlled OL-systems, termed cellworks, was introduced by A. Lindenmayer [8]. We provide an alternative definition of cellworks using markers, and use it as a formal basis for a simulation program. Cell geometry is viewed as the result of mechanical cell interactions due to osmotic pressure and wall tension. Developmental sequences can be animated by considering periods of continuous expansion delimited by instantaneous cell divisions. As an example, the method is applied to visualize the development of a three-dimensional epidermal cell layer.