Between 1890 and 1906, pioneering scientists in the Netherlands reached an understanding of phase separation and fluid mixture criticality that was far ahead of its time. This book narrates the story of these profound discoveries, and details the collaboration between two Dutch physicists and Nobel prize winners, Johannes Diderik van der Waals (1837-1923) at the University of Amsterdam, and Heike Kamerlingh Onnes (1853-1926) at the University of Leiden.