Critical illnesses include malignant tumors, serious cardiovascular diseases, illnesses that are likely to result in lifelong disability, surgeries requiring major organ transplants, and advanced chronic diseases. Major diseases usually refer to a broader range of diseases that often require huge medical expenses and will seriously affect the normal life and work of the patient and his/her family over a longer period of time. For example, malignant tumors, often excluding early malignant tumors such as carcinoma in situ; acute myocardial infarction, mostly caused by coronary artery ischemia and hypoxia resulting in necrosis of the myocardium; sequelae of stroke, often resulting in permanent dysfunction; and major organ transplantation or hematopoietic stem cell transplantation, which often requires allogeneic transplantation. There is also open-heart coronary artery bypass grafting; end-stage renal disease requiring dialysis or kidney transplantation; acute or subacute severe hepatitis; irreversible blindness; paralysis; severe Alzheimer’s disease; brain injury; Parkinson’s disease; and third-degree burns with 20% or more of the body surface area. Also included are severe motor neuron disease, severe aplastic anemia, open heart or open aortic surgery, severe multiple sclerosis, severe systemic lupus erythematosus nephropathy, and severe myasthenia gravis.