Historical note: Set theory was introduced by Georg Cantor, who was born in Russia in 1847. Cantor moved with his parents to Germany in 1856, studied at University of Berlin from 1863 to 1869, taught at the University of Halle from 1869 to 1905, and died in a mental hospital in Halle in 1918 (Reminding us that sometime there is a fine line between Genius and Madness). Cantor was the first to demonstrate the some infinite sets are "Larger" than others.