Over more than four years, the multidisciplinary CLASSY research and innovation action, which has been funded under the Horizon 2020 FET programme (now under EIC Pathfinder scheme), addressed the need for new technologies that have the potential to constitute an advancement towards sustainability and limited waste production of modern industrial synthetic processes. Inspired by the elegance with which living cells synthesise a large variety of complex components, CLASSY envisioned using the compartmentalisation strategy of cells to regulate chemical synthesis in a metabolic way.