The current approach to regulating mechanical properties of elastomeric materials is predominately based on the exploratory mixing of different polymers, solvents, and fillers-which is both inflexible in application and imprecise in property control. Here we overview a new materials design approach that harnesses well-defined molecular codes of independently controlled architectural parameters to program grand variation of mechanical "phenotypes". This design-by-iarchitecture approach generates a set of universal correlations between the molecular architecture and the physical behavior of elastomers. In turn, this will lead to novel solvent-free materials that closely mimic the mechanical behavior of biological tissues, ranging from soft fat tissue to firm skin, and fundamentally change high-impact technologies such as soft robotics, wearable electronics, and biomedical devices.