The liver is the biochemical powerhouse of the animal body. Most of the nutrients that the body absorbs from food go here first and are either stored or processed for distribution to other organs. All this work takes a lot of energy, and this is why the liver is dark red with fat-burning mitochondria and their cytochrome pigments. It also requires direct access of the liver cells to the blood, and accordingly there is very little connective tissue between the minute hexagonal columns of cells. It’s a delicate organ that is best briefly cooked; long cooking simply dries it out. The characteristic flavor of liver has been little investigated, but seems to depend importantly on sulfur compounds (thiazoles and thiazolines), and gets stronger with prolonged cooking. Generally, both flavor and texture coarsen with age. The occasionally milky appearance of chicken livers is due to an unusual but harmless accumulation of fat, about double the amount in a normal red liver (8% instead of 4%).