  Thin superconducting films form a unique platform for geometrically-confined,
strongly-interacting electrons. They allow an inherent competition between
disorder and superconductivity, which in turn enables the intriguing
superconducting-to-insulator transition and believed to facilitate the
comprehension of high-Tc superconductivity. Furthermore, understanding thin
film superconductivity is technologically essential e.g. for photo-detectors,
and quantum-computers. Consequently, the absence of an established universal
relationships between critical temperature ($T_c$), film thickness ($d$) and
sheet resistance ($R_s$) hinders both our understanding of the onset of the
superconductivity and the development of miniaturised superconducting devices.
We report that in thin films, superconductivity scales as $d^.$$T_c(R_s)$. We
demonstrated this scaling by analysing the data published over the past 46
years for different materials (and facilitated this database for further
analysis). Moreover, we experimentally confirmed the discovered scaling for NbN
films, quantified it with a power law, explored its possible origin and
demonstrated its usefulness for superconducting film-based devices.
