This article reviews the growing body of scientific work in Artificial Chemistry. First, common motivations and fundamental concepts are introduced. Second, current research activities are discussed along three application dimensions: modelling, information processing and optimization. Finally, common phenomena among the different systems are summarized. It is argued here that Artificial Chemistries are "the right stuff" for the study of pre-biotic and bio-chemical evolution, and they provide a productive framework for questions regarding the origin and evolution of organizations in general. Furthermore, Artificial Chemistries have a broad application range to practical problems as shown in this review.

Self-reproducing, cellular automata-based systems developed to date broadly fall under two categories; the first consists of machines which are capable of performing elaborate tasks, yet are too complex to simulate, while the second consists of extremely simple machines which can be entirely implemented, yet lack any additional functionality aside from self-reproduction. In this paper we present a self-reproducing system which is completely realizable, while capable of executing any desired program, thereby exhibiting universal computation. Our starting point is a simple self-reproducing loop structure onto which we "attach" an executable program (Turing machine) along with its data. The three parts of our system (loop, program, data) are all reproduced, after which the program is run on the given data. The system reported in this paper has been simulated in its entirety; thus, we attain a viable, self-reproducing machine with programmable capabilities. 1 Introduction The study of art...

Since von Neumann's seminal work around 1950, computer scientists and others have studied the algorithms needed to support self-replicating systems. Much of this work has focused on abstract logical machines #automata# embedded in two-dimensional cellular spaces. This research has been motivated by the desire to understand the basic information processing principles underlying self-replication, the potential long term applications of programmable self-replicating machines, and the possibility of gaining insightinto biological replication and the origins of life. Here we brie#y summarize the historical developmentof work on arti#cial self-replicating structures in cellular spaces, and then describe some recent advances in this area. Past research is viewed as taking three main directions: early complex universal computer-constructors modeled after Turing machines, qualitatively simpler selfreplicating loops, and e#orts to view self-replication as an emergent phenomenon. We discuss our own recent studies showing that self-replicating structures can emerge from non-replicating components and that genetic algorithms can be applied to automatically program simple but arbitrary structures to replicate. We also describe recentwork in which self-replicating structures are successfully programmed to do useful problem solving as they replicate. We conclude by identifying some implications and important research directions for the future.