Seedbanks store seeds and plant genetic material. The United States main seedbank is the National Seed Storage Laboratory (NSSL). The NSSL is part of the U.S Department of Agriculture's National Plant Germplasm System. In an article for Popular Science, Paul Raeburn described the NSSL saying " The jewel of the [National Plant Germplasm System] is the [NSSL], which lies in the shadow of the Rocky Mountains on the campus of Colorado State University in Fort Collins. Its walls may contain more biological wealth per square foot than anyplace else on earth...The NSSL is as much an archive as it is a laboratory. It is often described as the plant breeders' Library of Congress, offering an almost limitless selection of genetic traits for crop improvement. Because of its incalculable value to American agriculture, it is also sometimes called the plant breeders' Fort Knox" . To learn the NSSL's procedures for housing seeds take a tour of the NSSL. The NSSL holds roughly half a million seed plasm from 8,500 species, many from plants that can no longer be found in the wild. "Nature has installed a natural dormancy feature into seeds, which allows for their suspended preservation for long periods of time with little damage, provided the conditions are favorable," and that provides seedbanks with the opportunity to store seeds for several decades.