Figure 301 from Chapter 12 (Centrioles) of 'The Cell' by Don W. Fawcett M.D. Centrioles are usually positioned so that their long axes form a right angle. Their perpendicular orientation is maintained even though they may be half a micrometer or more apart and have no visible structural elements connecting them. The nature of the long-range forces or organization of the centrosomal cytoplasm that are responsible for this relationship are unknown. Departures from the usual orthogonal arrangement are occasionally encountered in normal cells and are reported to be common in malignant tumors. A copy of the chapter is available on the ASCB's BioEDUCATE website.