Coloured scanning electron micrograph (SEM) of cholesterol crystals (yellow) within a lipid droplet (purple) in a human liver. Cholesterol is a lipid that plays an important role in all animal cells and many body systems. It is produced by all animal cells, but in humans the majority is synthesised in the liver. The liver is also responsible for removing excess cholesterol. If the cholesterol cannot be removed quickly enough, such as in those with a high-cholesterol diet, it can accumulate in the liver causing fatty liver disease (steatosis). These accumulations may crystallise. The presence of crystallised cholesterol makes the progression from steatosis to the more serious, and sometimes fatal, condition nonalcoholic steatohepatitis (NASH) more likely. Magnification: x5000 when printed 10 centimetres tall.