Gamma was originally proposed in 1986 as a formalism for the de nition of programs without arti cial sequentiality. The basic idea underlying the formalism is to describe computation as a form of chemical reaction on a collection of individual pieces of data. Due to the very minimal nature of the language, and its absence of sequential bias, it has been possible to exploit this initial paradigm in various directions. This paper reviews most of the work around Gamma considered as a programming or as a speci cation language. A special emphasis is placed on unexpected applications of the chemical reaction model, showing that this paradigm has been a source of inspiration in various research areas. 1 The basic chemical reaction model The notion of sequential computation has played a central r^ole in the design of most programming languages in the past. This state of a airs was justi ed by at least two reasons: { Sequential models of execution provide a good form of abstraction of algorithm...