Flow chemistry enables reactions to be performed as a continuous process with precise control of reaction conditions such as temperature, pressure, and stoichiometry. Flow reactions can be performed in two regimes -continuous or slug flow. In continuous flow the entire fluidic system is filled with reagents, intermediate or formed product. Conversely in slug flow much of the fluidic system is filled with carrier solvent, small discrete reaction slugs then flow through the system (Figure ). Although slug flow reactions are being performed on a much smaller reaction scale, on a microfluidic scale the same reaction is performed. This means at identical positions within the flow reactor an identical profile is observed in both the slug and continuous flow regime. This linear scalability makes slug flow chemistry ideal for library synthesis in flow.