• Lysosomes contain numerous hydrolytic enzymes that allow them to degrade endocytosed materials or cytoplasmic structures such as old or damaged organelles. The process by which cells degrade their unneeded components is called autophagy.
• Peroxisomes contain oxidases and participate in detoxification reactions and Beta-oxidation of long chain fatty acids. Although they are abundant in metabolically active cells such as hepatocytes and cells of the kidney tubules, they are difficult to see in the LM without special stains.
• This material is sometimes visible by LM in routinely stained cells, such as the neurons and liver cells.
• The remains of lysosomes containing indigestible materials are called residual bodies or lipofuscin granules. These are sometimes visible as aggregates of brown staining material by LM in the cytoplasm of long-lived cells, such as neurons and liver cells.
• In TEM images, it can be seen that lysosomes (arrows, left image) vary in size and electron density, depending on what they are degrading. Peroxisomes (seen in the TEM image below, right image) are more uniform in size and electron density and sometimes contain a small region of increased electron density corresponding to their aggregated constituent enzymes.

Mitochondria