This chapter presents an artificial taxonomy of 2-D, self-replicating cellular automata (CA) that can be considered as proto-organisms for structure replication. We found that the process of self-reproduction is a widespread mechanism. In fact, self-reproducers in 2-D CA are very common and we discovered almost 10 methods of self-replication. The structures these systems produce, from ordered to complex ones, are very similar to those found in biological endeavor. After examining self-replicating structures and the way they reproduce, we consider their behavior in relation to the patterns they realize and to the function they manifest in realizing artificial organisms. According to us, many methods produced by CA are based on universal models of biological cell development. The relevance of such work consists in the goal of modeling the evolution of living systems that can lead us to a better understanding of the essential properties of life.