Imagine a world without smartphones or where modern cancer treatments and mRNA vaccines are just a dream, and NASA’s James Webb Space Telescope never left the ground. What about a world without pacemakers, where nanotechnology research was impractical, and high-precision camera lenses were so riddled with defects they were, well, not high precision. That would be a world without cleanrooms. Stepping into an ISO Class 1 cleanroom, for instance, is something like entering another world, where the air you breathe is thousands, if not millions, of times cleaner than a typical office or home. An outdoor urban space has somewhere in the ballpark of 35 million particles per cubic meter.