Martin Odersky was doing deep theoretical work in functional programming when Sun Microsystems released Java. Realizing that Java changed the playing field for language development, he created Scala, a language that brought functional features to the Java infrastructure. The result was a language that leverages the JVM and its libraries and allows programmers to use object-oriented or functional approaches at will—a true hybrid language. Twitter and Foursquare were among Scala’s early adopters.