Systems Biology is a scientific discipline combining experimental or field research with theoretical or computational approaches. The ultimate goal of this discipline is to understand what kind of different outcomes can arise from the interactions and the processes happening in biological systems such as ecosystems, cellular pathways, or host-pathogen relations. Most of these interactions are highly nonlinear and thus a wide array of dynamical behaviours and different transitions are typically found. Systems biology has deeply entered into the field of pathogens' dynamics and evolution, and multitude of research has proved that viruses, bacteria, and other pathogens undergo evolutionary- and ecologically-grounded processes. These processes determine the fate of pathogens and their evolutionary potential during infection. In a similar way, synthetic biology is aimed at understanding how novel (synthetic) processes can modify biological functions. Both modelling and computational approaches are also used in this scientific field to understand and predict the behaviour of synthetic and natural biological systems.