Compartmentalization is well documented in biocatalysis as a method for achieving efficient in vivo tandem catalysis by confining and separating enzymes in well-defined micro-and nanostructures. By compartmentalizing catalysts, biocatalysts benefit from substrate and product trafficking, retention of reactive or toxic intermediates, increased reaction rates to high local substrate concentrations, and mitigation of deactivating or competing pathways. For example, carboxysome microcompartments accelerate CO2 fixation by encapsulating the carbonic anhydrase and ribose 1,5bisphosphate carboxylase/oxygenase cascade to generate high local concentration of CO2 and exclude deactivating O2. With billions of years of evolution, compartmentalization maintains a key role in biology's efforts to manage the complex network of competing and incompatible biochemical reactions.