Dear all, from the Volume Visualization Tour, I discovered the topography command that now allows me to dsiplay atomic force microscopy data (basically bitmap images with grey scales representing height). In that way I got some very nice images. I also found out how to scale the voxel size, so the scale of the structures should be correct. To test this, and to be able to add some length markers, I wanted to measure distances on the surface generated by the topography command. But while that seems possible for volume data (by setting markers), I had no success with the surface representation of my data nor the original image (which is handled as kind of a volume, but a single slice) when it came to setting markers or measuring distances in another way. Did I miss anything, or is that just not possible? I am using build number 2509, because of the topography feature. Setting markers is described as working by setting the marker in the first maximum in the line of sight at the click position. For surfaces, you could just take the position of the visible pixel clicked. Or maybe it is possible to convert surfaces to volumes? Thank you for your help Daniel Hautzinger