Cleanrooms have been an evolution of necessity, originating out of the medical field around the 1860s with the observation of bacteria, and resulting understanding that bacterial exclusion in operations, greatly improve recovery rates. This was one of the starting points of aseptic methods around the world and subsequent cleanroom development.
During World War Two there was another major development in cleanroom requirements. No longer was it only exclusion of bacteria from wounds that was of interest, but large failure rates of equipment were costing lives, and the exclusion of particles from equipment research and equipment manufacture was required.
Although the medical, pharmaceutical and defence fields still require high level cleanrooms, today exclusion of particles is not necessary for all high tech or life threatening fields. The principals developed in cleanroom design and construction are used in fields as diverse as keeping instruments clean and operational in open cut mining to the paint job on your new car and even the food and beverage industry.