 Characteristic of the search for design principles in modern systems biology is that the strategy is enforced through automated pattern-detection in network models based on large biological datasets, as exemplified by the search for network motifs  (Section 1.1.1).  The hope is that simple control principles, using e.g., positive and negative feedback, can make up basic building blocks of biological functioning such as filters, switches, oscillators, amplifiers, detectors etc. (Alon 2007; Tyson et al. 2003). One such example is the so-called toggle-switch, a simple regulatory circuit that is considered a design principle in both systems and synthetic biology.