Controlled substances are drugs or chemicals that are regulated by law due to their potential for abuse or addiction. These substances are classified into different schedules based on their medical use, safety, and potential for dependency. For example, Schedule I substances, like heroin, have no accepted medical use and a high potential for abuse, while Schedule II substances, such as morphine, have accepted medical uses but can still lead to severe dependence. The regulation of controlled substances is managed by agencies like the Drug Enforcement Administration (DEA) in the United States. These regulations help ensure that medications are prescribed and dispensed safely, minimizing the risk of misuse. Healthcare providers must follow strict guidelines when prescribing these substances to protect public health.