Ruddlesden-Popper phase metal-halide perovskites (RPPs) have attracted significant attention in recent years due to their promising light harvesting and emissive properties. In the past 5 years alone, RPPs have enabled LEDs and solar cells with competitive operational stabilities and efficiencies. In my talk I will discuss my PhD work on the physical and electronic structure of RPPs. I will briefly discuss how RPPs are formed; how their kinetics of formation determine their composition and orientation; the implications of their composition and orientation; and how this understanding could be used to improve optoelectronic devices. I will then discuss our work on the band alignment of RPPs in the context of a disagreement within the metal-halide perovskite community; and the implications of this band alignment on charge transfer and optoelectronic devices. Ultimately, our work could help improve understanding of this material class, and support research to improve device performance and stability. References:R. Quintero-Bermudez et al., J. Phys. Chem. Lett., 11, 4213 (2020).R. Quintero-Bermudez et al, J. Am. Chem. Soc., 141, 13459 (2019).R. Quintero-Bermudez et al., Nature Materials, 17, 900 (2018).