Matthias Felleisen is a German-American computer science professor and author. He grew up in Germany and immigrated to the US when he was 21 years old. He received his PhD from Indiana University under the direction of Daniel P. Friedman. After serving as professor for 14 years in the Computer Science Department of Rice University, Felleisen joined the Khoury College of Computer Sciences at Northeastern University in Boston, Massachusetts as Trustee Professor. Felleisen's interests include programming languages, including software tools, program design, software contracts, and many more. In the 1990s, Felleisen launched PLT and TeachScheme! (later ProgramByDesign and eventually giving rise to the Bootstrap project ) with the goal of teaching program-design principles to beginners and to explore the use of Scheme to produce large systems. As part of this effort, he authored How to Design Programs (MIT Press, 2001) with Findler, Flatt, and Krishnamurthi. For his dissertation Felleisen developed an extension of Church's lambda calculus with assignment statements and continuation operators. The dissertation re-proved the Church-Rosser theorem and the Curry-Feys Standardization Theorem for these extended calculus. It thus established a novel form of operational semantics for higher-order functional languages with imperative extensions. Its most well-known application is for a proof of type safety, worked out with his PhD student Andrew Wright. Tim Griffin showed a few years later that Felleisen's lambda calculus with continuation operations is in a Curry-Howard correspondence to classical logic, a controversial insight at the time. In a similar vein, Barker and Shan connected continuations and especially Felleisen's delimited continuations calculus the linguistic concepts via Montague grammars. Part I of "Semantics Engineering with PLT Redex" is derived from his dissertation. Control delimiters, the basis of delimited continuations, were introduced by Felleisen in 1988. They have since been used in many domains, particularly in defining new control operators; see Queinnec for a survey. A-normal form (ANF), an intermediate representation of programs in functional compilers were introduced by Sabry and Felleisen in 1992 as a simpler alternative to continuation-passing style (CPS). An implementation in the CAML compiler demonstrated its practical usefulness and popularized the idea With Findler, Felleisen developed the notion of higher-order contracts. With such contracts, programmers can express assertions about the behavior of first-class functions, objects, classes and modules. Felleisen's work on gradual typing was a direct continuation of his work on these contracts; see below. In support of the TeachScheme! project, Felleisen and his team