Steatosis is the abnormal accumulation of fat inside the cells of an internal organ, most commonly the liver — fatty liver disease. It develops when the rate at which the organ takes up or makes fat exceeds its ability to burn or export it. Causes include excessive alcohol consumption, obesity and insulin resistance, certain medicines, and exposure to toxins. In its early stages it is reversible and may cause no symptoms, but if the underlying cause continues, inflammation and scarring can follow, progressing toward cirrhosis. Diagnosis is usually by blood tests, ultrasound, or biopsy. Management centres on removing the cause: reducing alcohol, losing weight, controlling diabetes, and avoiding substances that harm the liver.