The Food and Drug Administration (FDA) is a federal agency of the United States Department of Health and Human Services. Its primary responsibility is to protect public health by ensuring the safety, efficacy, and security of human and veterinary drugs, biological products, medical devices, food, cosmetics, and tobacco products.

The FDA is responsible for regulating all aspects of drug development, from preclinical research to clinical trials and post-market surveillance. It reviews applications for Investigational New Drugs (INDs), New Drug Applications (NDAs), and Biologics License Applications (BLAs), and it approves or rejects these applications based on the safety and efficacy of the product.

The FDA also regulates medical devices, including diagnostic tests, surgical instruments, and implantable devices. It reviews applications for premarket approval (PMA) of high-risk medical devices, as well as premarket notification (510(k)) for low to moderate-risk medical devices.

In addition to its regulatory functions, the FDA conducts research to improve its understanding of the safety and efficacy of products it regulates. It also works with other federal agencies, such as the Centers for Disease Control and Prevention (CDC), to respond to public health emergencies and outbreaks.

The FDA is a critical component of the US healthcare system, as it helps to ensure that products are safe and effective for patients. Its regulatory oversight of drugs, medical devices, and other products helps to protect public health and promote access to high-quality healthcare.