100 years of research history

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In the early 20th century, research activities on negative ions started in Germany, Russia, and some other countries, but many were disrupted by the WWII.

Extensive research was conducted in Japan during the 1930s at universities, in particular at Hokkaido University, and in laboratories. A number of theories were established during this period. Research had only been conducted by a small number of researchers until the late 1990s when negative ions started attracting more attention.