Figure 240 from Chapter 7 (Mitochondria) of 'The Cell, 2nd Ed.' by Don W. Fawcett M.D. The shape of mitochondrial cristae can vary with cell type, shown here in a cell from hamster adrenal cortex. For example, thin folds of the inner membrane are the most common configuration, but they may take on a tubular form (see the end-on profiles indicated by arrows in this figure). Lamellar stacks are common in fetal and neonatal tissues, but may persist in parts of the mitochondrion even in mature cells (see arrow labeled with X). A PDF copy of the accompanying chapter is available on the ASCB’s BioEDUCATE website.