Materials define progress. Organic-inorganic hybrid materials based on the perovskite crystal structure have recently attracted a great deal of attention in the field of new and emerging photovoltaics, where photo-conversion efficiencies of over 15% have been demonstrated (with independent verification at 14.1%). These recent developments are the first examples of a truly low-cost photovoltaic system based on earth-abundant materials yielding efficiencies that are competitive with traditional photovoltaic technologies. It was recently shown that photovoltaics based on hybrid perovskites can operate in a thin-film architecture. The thin-film architecture enables simplified processing, potentially better control, provided the method of processing is carefully chosen, and a greater availability of analytical tools compared to solution processing. Crucially, it is possible to transfer over 30 years of existing, proven thin-film photovoltaic technology into the new system such as photonic management in light-trapping techniques and a whole host of electronic contact engineering knowledge thus rapidly progressing State of the Art.Understanding thin-film formation and properties is paramount to the development of this technology beyond the State of the Art. The application of advanced thin-film deposition techniques such as pulsed-laser deposition allows the formation of atomically smooth films and crucially it allows control over the material stoichiometry and composition, thereby enabling control over material properties. Furthermore, sophisticated instrumentation to monitor thin-film growth in-situ thus allowing the researcher to carefully probe the processes in thin-film formation exists. Another imminent challenge is to gain control over the material crystallisation and film formation, achieving this will lead to better reproducibility thus help devise realistic industrial scale-up strategies