The substitution of atoms by molecules in the structure motifs of all-inorganic materials is a powerful approach for designing new materials. It opens up a large chemical design space for studying application-oriented and fundamental 2 structureproperty relationships, while still allowing the use of established principles from inorganic solid-state chemistry to guide materials discovery. For instance, in coordination polymers that crystallise in an AMX3 perovskite motif, such as [CH3NH3]Mn(N3)3 and [C10H20N]Cd(C2N3)3, here referred to as molecular perovskites, properties such as ferroelastic, (improper) ferroelectric and multiferroic behaviour, their glass-forming abilities and their application as barocalorics are linked to the molecular nature of the A-and X-site. In molecular perovskites, a ReO3-type [MX3] -network is formed by the M-site cation (M 2+ ) and X-site anion (X -) with the A-site cation (A + ) sitting in the void of the pseudocubic [MX3] - network for charge balance (Fig. ).