The National Institutes of Health (NIH) is the primary federal agency responsible for medical research in the United States. Its mission is to seek fundamental knowledge about living systems and apply that knowledge to enhance health, lengthen life, and reduce illness and disability. In practical terms, this means NIH funds the majority of publicly supported biomedical research in the country, runs its own laboratories, and provides free health information to the public.
How NIH Is Organized
NIH is made up of 27 separate institutes and centers, each focused on a particular area of medicine or science. Some of the largest and most recognizable include the National Cancer Institute, the National Heart, Lung, and Blood Institute, and the National Institute of Allergy and Infectious Diseases. Others focus on areas like diabetes and kidney diseases, mental health, aging, and child development. The National Institute of General Medical Sciences supports basic biological research that doesn’t fall under a single disease category but lays the groundwork for future treatments across many fields.
This structure means NIH isn’t one monolithic lab. It’s more like a network of specialized agencies, each with its own director, budget, and research priorities, all operating under one umbrella. Jay Bhattacharya became the 18th NIH director on April 1, 2025.
Funding Research Across the Country
The bulk of what NIH does is fund other people’s research. Most NIH-supported studies happen at universities, medical schools, and research hospitals across the United States and in some foreign countries. Scientists at these institutions apply for grants through a competitive process, and if selected, NIH pays for their work. This is called extramural research.
NIH also conducts intramural research, meaning studies done by scientists employed directly by the federal government. Most of these researchers work on the NIH campus in Bethesda, Maryland. The intramural program gives NIH the ability to pursue long-term, high-risk projects that might not survive the typical grant cycle at a university.
The FY 2027 budget request for NIH is $41.4 billion. In fiscal year 2023, every dollar of NIH funding generated approximately $2.46 in economic activity, reflecting how research spending ripples outward through universities, biotech companies, and local economies.
How NIH Chooses What to Fund
NIH doesn’t hand out grant money casually. The process is built around peer review, where working scientists evaluate each other’s proposals before any funding decision is made. At least three reviewers are assigned to each application. They read it thoroughly, write critiques summarizing its strengths and weaknesses, and assign a preliminary score.
During a review meeting, the primary reviewer presents the application to the full panel, the other assigned reviewers add their perspectives, and all eligible panel members discuss and score the proposal. NIH uses a 9-point scale where 1 is exceptional and 9 is poor. Final scores are averaged and multiplied by 10, producing overall impact scores ranging from 10 (highest impact) to 90 (lowest). Applications that the panel unanimously considers less competitive, typically the bottom half, aren’t discussed at all and receive no numerical score.
After the meeting, each reviewed application gets a summary statement that includes the impact score, a written summary of the discussion, and the assigned reviewers’ detailed critiques. This system is designed to ensure that funding decisions are driven by scientific merit rather than institutional prestige or politics.
Major Breakthroughs Tied to NIH
Decades of NIH-funded work have contributed to some of the most significant advances in modern medicine. In the 1960s, NIH researchers discovered how the genetic code in DNA gets translated into proteins through messenger RNA. That discovery touched nearly every branch of science, from understanding inherited diseases to developing new drugs.
NIH-supported scientists also adapted green fluorescent protein (GFP), a molecule that makes jellyfish glow, into one of the most widely used tools in biology. GFP lets researchers watch living cells in real time, tracking everything from cancer growth to brain activity. The work earned a Nobel Prize in Chemistry in 2008. Two years earlier, in 2004, two NIH-supported researchers won the Nobel Prize in Physiology or Medicine for mapping how the human sense of smell works, revealing that we have roughly 400 types of odor receptors.
More recently, decades of NIH investment in basic science, including research originally aimed at HIV, led directly to the mRNA vaccine technology behind the first two FDA-approved COVID-19 vaccines. Both the Moderna and Pfizer/BioNTech vaccines used a spike protein sequence discovered by NIH scientists and their collaborators. NIH research also pioneered enzyme replacement therapy for rare genetic disorders. Work on Gaucher disease, where enzyme deficiencies cause harmful waste buildup in cells, led to the first enzyme replacement therapy approved by the FDA in 1991 and became a model for treatments now approved for 11 different disorders.
Free Health Information for the Public
Beyond funding and conducting research, NIH maintains some of the world’s largest public health databases. PubMed, run by the National Library of Medicine, contains more than 40 million citations for biomedical literature, with links to full-text articles when available. It’s used daily by doctors, researchers, students, and increasingly by patients who want to read the actual science behind their diagnoses.
MedlinePlus, another NIH resource, translates that research into plain-language health information covering thousands of conditions, medications, and medical tests. ClinicalTrials.gov lists ongoing and completed clinical studies, letting patients and doctors search for experimental treatments. These tools make NIH not just a research funder but a direct source of health information for anyone with an internet connection.