Organ donation involves removing tissues or organs from a living or recently deceased person for transplantation into another person. People of all ages can donate organs, and donation can occur from both living and deceased donors, though deceased organ donation provides access to more organs and must be transplanted within hours. While organ donation is voluntary in most places, systems can be opt-in, where explicit consent is required, or opt-out, where consent is assumed unless the deceased registered refusal. Common organs for donation include kidneys, liver, heart, lungs, pancreas, and corneas. However, organ shortages persist due to lack of family consent and negative public attitudes sometimes related to religion, fear, or misunderstanding.