Fuel cell technology is currently emerging as a promising option for efficient and flexible energy production. Proton Exchange Membrane Fuel Cells (PEMFCs) are distinguished as a suitable solution for many sectors, including residential, road transport and industrial applications due to their high efficiency, low operating temperature and fast start-up times. In this framework, the present study presents a detailed experimental characterization of a small-scale PEMFC through a reverse engineering approach. A Horizon H-500 fuel cell was subjected to a comprehensive series of experimental tests, which included polarization curve analysis and electrochemical impedance spectroscopy, to assess its efficiency and operational behavior under different conditions. Once the validity of the recorded data is verified, the fuel cell has been disassembled and each subcomponent has been used for a comprehensive understanding of the main structural parameters that are often assumed or derived from literature in numerical models, i.e., the dimensions and configuration of reactant distribution channels. Following the experimental characterization, a 0D/1D model of the fuel cell was developed using the commercial software GT-POWER. This model has been validated against the laboratory data, including power and polarization curves and structural parameters to ensure its accuracy in reproducing real-world performance. Once validated, the model has been used to conduct parametric analysis, evaluating the sensitivity of the model to the key parameters affecting the overall performance of the fuel cell system. The results of this study provide insights into the influence of individual components on system efficiency, contributing to a better understanding of fuel cell design, optimization of strategies and highlighting the potential of reduced-order modeling to accelerate the research & development (R&D) by simplifying the complex phenomena otherwise not observable.