Leiden University at the university. The learning and reputation of Jacobus Gronovius, Herman Boerhaave, Tiberius Hemsterhuis and David Ruhnken, among others, enabled Leiden to maintain its reputation for excellence down to the end of the 18th century. At the end of the nineteenth century, Leiden University again became one of Europe's leading universities. At the world’s first university low-temperature laboratory, professor Heike Kamerlingh Onnes achieved temperatures of only one degree above absolute zero of −273 degrees Celsius. In 1908 he was also the first to succeed in liquifying helium and can be credited with the discovery of the superconductivity in metals. The
Tettje Clay-Jolles 1903 when she transferred to the University of Leiden. She was one of the few women who studied physics at the university. There she began her doctoral research on low-temperature physics under Heike Kamerlingh Onnes. She worked on her thesis until December 1908 when she left her studies to devote herself to her family. Clay-Jolles met and fell in love with Jacob Clay, another of Kamerlingh Onnes's students, and in 1908 the two were married. Later that year she left school to focus on her family. She spent the next twelve years raising the couple's three children. In 1920 the