High-magnification transmission electron micrograph of a hepatic sinusoid of rat liver, fixed by perfusion-fixation with glutaraldehyde, postfixed in osmium, dehydrated in alcohol, and embedded in Epon (reference). The lumen of the sinusoid (L) is lined by the endothelium (E), showing the presence of fenestrae (small arrows) and coated pits (asterisks). Note a lipid particle (large arrow) which passed the fenestrae, illustrating the sieving effect of fenestrae. The space of Disse (SD) contains numerous microvilli of the parenchymal cells (P). (Courtesy of Drs R. De Zanger, reference ). Scale bar, 300 nm.