Fuel cells are complex three dimensional electrochemical devices composed of multiple materials with features spanning many orders of magnitude. While they are increasingly used for both mobile and stationary power generation, the performance of the devices is intricately linked to the details of the internal microstructure. However, since they operate in non-ambient conditions, detailed investigations into microstructural evolution have historically been very difficult. In this webinar we discuss how advanced ZEISS microscopy techniques can reveal complex ageing and degradation mechanisms in polymer electrolyte fuel cells and pave the way towards advanced device development.