The following document deals with the hierarchical data structure pyramid for three-dimensional data, which is used to speed up the visualization process or for necessary preparations like data registration. [9] contains an overview of methods for speeding up the visualization, also hierarchical data structures like the pyramid. In the following descriptions a voxel is one data point and a cell consists of 8 eight adajcent voxels, which are arranged as a cube (uniform samples). The differences of voxels and cells, which are associated with volume visualization are not used.