My research interest are in the unification of the fundamental matter and interactions. I have pursued this interest in two directions. The first is the construction of quasi-realistic string models that reproduce the gross structure of the Standard Model, as well as finer details in specific models and scenarios. The relevant class of string compactifications correspond to Z2xZ2 orbifolds of six dimensional toroidal lattices. In addition to producing a large space of phenomenological string models, they exhibit a rich mathematical structure, which is of interest in its own right. This mathematical structure relates to the properties of K3 surfaces and their symmetries, including the emerging interest in Moonshine symmetries and modular forms. Ultimately, the aim is to explore how this mathematical structures play a role in the phenomenological properties of the quasi-realistic string vacua. The second direction entails the study of duality symmetries in quantum mechanics, quantum field theories and string theory. This interest led to the formulation of quantum mechanics from an equivalence postulate. The aim is to extend this formalism of quantum mechanics to a formalulation of quantum gravity.