Model forms most useful

It is becoming increasingly evident that the key to unraveling complex genotype-environment-phenotype relations lies in understanding the principles of emergence in bio-molecular interaction networks. Darwin's tangled bank contemplation [1] provides, through the theory of evolution, an elegant basis for how model organisms can help untangling this complex relationship. Indeed, the use of model organisms has been instrumental for expanding our knowledge about life. This goes back to the early days of molecular biology where the gut bacterium Escherichia coli was used to gain insights into gene regulation, first demonstrated by pioneering studies of the lac-operon by Jacob and Monod [2]. It is therefore also not surprising that key model organisms were among the first to have their genome sequenced, e.g. Caenorhabditis elegans[3], Saccharomyces cerevisiae[4] and E. coli[5], and yeast as a general eukaryotic model organism has also been used to demonstrate many of the high-throughput experimental techniques that today are among the foundation for systems biology [6]. With advancement in experimental techniques, the model organisms presently in use span, like the life on a tangled bank, several domains of life, from bacteria to mammals, offering a model system for addressing most topical questions in systems biology.