The Mir and Spacelab programs provided only a glimpse. Critics doubt that it can. NASA argues that the nascent station someday will yield plenty of scientific breakthroughs in areas ranging from medicine to engineering. They just can't say what those might be or when they will come. As supporters see it, that sort of hedging is no different than the expectations for any general research laboratory on Earth.
Some results are fairly dramatic and come early.
Other times, it takes a long time. The earliest results no doubt will come in learning how to operate and live safely aboard large structures in orbit. Long-term investigations, such as understanding how and why certain bodies of water are drying up on Earth, probably won't be conclusive for years. Breakthroughs, if and when they happen, often are the result of basic research done years before. This black and white image shows the view from Russian TV as Progress docked with the International Space Station.