In May 1948, the unmanned research balloon on Popular Science's cover lifted off to explore the stratosphere. As part of Project Skyhook, researchers from General Mills—yes, that General Mills—loaded the balloon with instruments, and deployed it to 100,000 feet to analyze air composition and cosmic rays. "Where our balloons now float will be man's highway of tomorrow," Otto C. Winzen, the project's engineer, told us then. Now, companies are racing to prove Winzen's prediction correct. They plan to lift tourists to 100,000 feet using football-field-size balloons that drift on a path over Earth before descending. Read more about how they'll do it here.