Anesthesia problems, such as pneumonia, blood clots, and, in rare cases, death, are possible consequences for any surgical treatment. Infection at the location of the incision may increase scarring and necessitate further surgery. Freezing of tissue or nerves is another risk with any form of surgery. A frozen tissue will usually require removal by further surgery. Plastic surgery involves the permanent change of some aspect of the face or body through an operation. Many different procedures exist that can be used to improve certain features, alter physical characteristics, correct deformities, and more. Some forms of plastic surgery are: breast augmentation, breast reduction, chest reshaping, arm lift, facial sculpting, eyelid surgery, nose reshaping, necklift, abdominoplasty (tummy tuck), and penile enhancement (girth and length). The safety of plastic surgery has improved greatly over time. Modern anesthesia techniques are very safe when administered by experienced physicians. Other factors that affect its safety include the patient's age, health, history of disease, type of procedure performed, and the facility where it is done. Bodies were originally made of flesh that healed if not damaged. Today, bodies are mostly made of bone that cannot heal itself. The only way to heal bone is by using bone grafts from elsewhere in the body.