Microscopic swimmers, like bacteria, spermatozoa and algea, have been studied extensively. Models have been created to understand how they move in different enviroments, how they effectively find food, and how does this relate to our cellular development and evolution. In this presentation I will discuss two of my recent efforts of mine to extend such modelling to understanding more complex systems. In the first we will look at how a simple swimmer model (Taylor’s swimming sheet) can be extended to understand more about filter-feeding microorganism (choanoflagellates). The second topic will then explore how bacteria behaviour studies can help us quantify and understand the behaviour of the earliest prehistoric organisms.