What did Vincent J. Schaefer discover when dry ice was dropped into a cloud in a laboratory freezer?

In 1946, while conducting experiments at the General Electric Research Laboratories, Vincent J. Schaefer discovered that when dry ice pellets were dropped into a cloud composed of water droplets within a laboratory freezer, the water droplets were rapidly replaced by ice crystals. These crystals subsequently increased in size and fell to the bottom of the container.1

This observation demonstrated that supercooled clouds—those containing water droplets at temperatures below freezing—could be artificially dissipated by seeding them with ice nuclei. This discovery marked the beginning of the modern era of scientific weather modification.12