Three Americans won the Nobel Prize in Physiology or Medicine on Monday for discovering the machinery that regulates how cells transport major molecules in a cargo system that delivers them to the right place at the right time.

The Karolinska Institute in Stockholm announced the winners: James E. Rothman, 62, of Yale University; Randy W. Schekman, 64, of the University of California, Berkeley; and Dr. Thomas C. Südhof, 57, of Stanford University. Their basic research solved the mystery of how cells, which are factories producing molecules, organize a system to transport the molecules within cells and export them outside.

As it turns out, the molecules are moved around the cell in small packages called vesicles, and each scientist discovered different facets of what is needed to ensure that the right cargo is shipped to the correct destination at precisely the right time. For example, pancreatic cells make insulin and release it in the blood. Chemical signals called neurotransmitters are sent from one nerve cell to another to allow people to walk, talk, sing, pull their hand away from a hot stove and communicate. The molecular traffic within cells is as complicated as rush hour in any city, as the discoveries by the three Nobel winners revealed.

The world’s most prestigious scientific award arrived at a particularly dark time for federal science research: the National Institutes of Health, the agency that paid an estimated $49 million to help underwrite the winners’ work, has been forced to send home most of its staff because of the government shutdown. Basic research of the type that just won the Nobel is seen as particularly vulnerable to Capitol Hill budget cutters.