Colored scanning electron micrograph of brown human hepatocytes and a yellow Kupffer cell (a type of liver-specific macrophage) surrounded by red blood cells. Hepatocytes and Kupffer cells line the capillaries of the liver. Liver cells secrete bile, which is carried through the canaliculi (shown in yellowish green) to be stored in the gallbladder. Image: © Prof. P.M. Motta, Sapienza University of Rome/Science Photo Library.