Benign by Design (BbD) aims to conserve material resources and the environment effectively by considering the end-of-life stage of chemicals/materials/products already at the early design phase. This chapter focusses on designing chemicals/pharmaceuticals for full mineralization after their introduction into the environment at the end of their life. Exemplified are BbD principles, biodegradable compounds, (re)design approaches, and testing strategies. An important principle is, e.g., that biodegradability depends on the ambient conditions, which change along compounds’ lifecycle. This exemplification will encourage BbD’s application. Bringing BbD into practice dependents on available test methods and knowledge. Interdisciplinary collaboration and training are key.