This is how I figured out a rough method for data collection with a BioRad MRC 600 for volume rendering with VoxelView. We are using Nikon 60X NA 1.4 objective, 1 1/2 coverslips, and glycerol / PBS/ n-propyl gallate mounting medium. I expected the Z axis to be incorrect because of index of refraction problems, but this is not what I found. A user brought cell cultures to our facility for confocal. One of the stains was for f-actin. There were a lot of dividing cells. Viewing from above, conventionally or w/ single optical section, cells in metaphase appeared to be circular regardless of orientation and uniform in size. Thus, we assumed the cells were close to spherical. We set the Z step to a multiple of the X,Y resolution and interpolated accordingly (e.g. X, Y 0.1 um, Z step 0.3 um, interpolate twice). With 25 um diameter cells, this takes a long time! -Michael C.