Even in humans, some cells (e.g., capillary endothelial cells) may contain peroxisomes with a marked crystalloid matrix. Peroxisomal proteins, including enzymes, are synthesized by free polysomes of the cytosol and then transported into peroxisomes.

Though peroxisomes, unlike mitochondria, have no genetic material of their own, it is considered that the organelles are able to divide or bud off like mitochondria do. The image depicts a fragment of a metabolically active endothelial cell in a capillary. One may distinguish some dilated cisterns of rough and smooth endoplasmic reticulum, mitochondria, such cytoskeletal elements as microtubules and intermediate filaments, as well as basement membranes of the endothelium and of pericytes.