The operating microscope revolutionized surgery in the second half of the 20th century, but the first prototype was built back in 1921 by Carl-Olof Siggesson Nylén from the University of Stockholm. His and his descendants' work allowed doctors to perform operations on structures smaller than 1 mm, like vessels and nerves. Microsurgery was crucial to for example neurosurgery, but it also made all surgical procedures much more efficient, drastically shortening time of hospitalization following operations.