Figure 239 from Chapter 7 (Mitochondria) of 'The Cell, 2nd Ed.' by Don W. Fawcett M.D. The cristae of mitochondria can take on zig-zag configuration (see arrows) which is particularly apparent in cells of metabolically active tissues like skeletal and cardiac muscle. These panels show mitochondria from cat ventricular papillary muscle. A PDF copy of the accompanying chapter is available on the ASCB’s BioEDUCATE website.