Figure 238 from Chapter 7 (Mitochondria) of 'The Cell, 2nd Ed.' by Don W. Fawcett M.D. Mitochondria from brown adipose cells can attain a diameter of 5 to 7 µm (for scale, compare with the portion of nucleus apparent to the left of the image). In these cells, the cristae can be seen traversing the entire width of the mitochondrion, with fenestrations at the junction with the inner membrane, preventing the matrix from separating into multiple isolated compartments. A PDF copy of the accompanying chapter is available on the ASCB’s BioEDUCATE website.