The theory of quantum electrodynamics (QED) describes the intricacies of atom-light interactions with great accuracy, however, viewing a system via fully-microscopic lens can in certain instances be counter-productive. For example, we can consider a quantum system (containing atoms) which encounters a macroscopic surface (made of astronomical number of atoms). It is then advantageous to describe such a system utilising a modified framework, called macroscopic QED. Given a large enough distance between a test atom and a surface, we can abstract away the constituent atoms of the object replacing it with an emergent entity, a familiar classical surface described by its electric permittivity. This thesis explores the relationship between structures and physical observables, considering the notion that a macroscopic surface influences the nature of the electromagnetic field. We examine both classical and quantum properties of fields and atoms, utilising two distinct approaches to geometry design. First, we employ and adapt a reverse-engineering protocol, wherein structures are discovered algorithmically without input from a human designer. This is particularly beneficial in systems where no discernible intuitive design can be formulated, resulting in purpose-driven structures with superior performance, often featuring the appearance of seemingly-random characteristics. Second, we investigate conventional structures whose stationary effects on atoms (electrostatic potentials) are known analytically from antenna design. We apply these to novel scenarios in the quantum realm, measuring the impact on atomic properties, both for intrinsic interest and applications in sensing.