Hydrogen produced by electrolysis using renewable electricity, known as green hydrogen, is both a promising energy vector and a future feedstock for decarbonisation. To achieve widespread adoption, it is essential to reduce the production cost of green hydrogen, which requires the development of efficient, low-cost electrolysers. Among low-temperature water electrolysis technologies, alkaline water electrolysis (AWE) is the most mature but suffers from high internal resistances and responds too slowly for dynamic operation, making it less suitable for coupling with intermittent renewable energy sources. In contrast, proton exchange membrane water electrolysers (PEMWEs) offer higher efficiency and dynamic operation capabilities thanks to their solid polymer electrolytes, but are costly due to the need for platinum group metal (PGM) catalysts. Anion exchange membrane water electrolysers (AEMWEs) combine the strengths of both AWEs and PEMWEs and therefore have the potential to reduce the cost of green hydrogen. The alkaline environment means the material costs are lower than for PEMWE, while the hydroxide conducting solid polymer electrolyte significantly reduces the internal resistance compared to AWE. Like PEMWE, the use of a membrane means the hydrogen produced is high purity and dynamic operation is possible. Of the three low-temperature electrolyser technologies, AEMWE is at the earliest stage in its development, sitting at Technology Readiness Level 6 according to the International Energy Agency. State-of-the-art AEMWEs still have relatively poor durability, with lifetimes of 1000-3000 h; PEM systems, meanwhile, run for >10,000 h and AWE >100,000 h. Most of the research efforts on AEMWEs have been devoted to developing conductive and durable anion exchange membranes and ionomers as well as highly active PGM-free catalysts for both alkaline oxygen and hydrogen evolution reactions (OER and HER respectively). Despite considerable improvements in AEMWEs, long-term durability remains the pertinent issue. Anion exchange polymers, consisting of a backbone with cationic functional side chains, often have poor chemical stability when used as AEMs and ionomer binders and thus, their durability at high pH has been extensively studied. The degradation of these polymer materials can have conflicting effects on the measured cell potential (Ecell) depending on the degradation pathway. For example, the quaternary ammonium cationic functional groups that typically give AEMs their hydroxide-conducting properties are susceptible to nucleophilic attack by hydroxide ions. The loss of cationic functionality, and resulting decrease in ionic conductivity, increases ohmic resistance in the cell and results in a higher Ecell. Ionomer binders, often made of the same polymer as the AEM, are used to physically adhere the catalyst to the AEM or porous transport layer (PTL) and to ionically connect the catalyst to the AEM. Breakdown of the ionomer during the operation leads to catalyst detachment from the membrane or PTL. Detachment of the catalyst has two main effects: firstly, the number of active sites is reduced which causes the reaction rate to decrease, and secondly; the remaining catalyst has reduced contact with the AEM, resulting in higher ohmic resistance. Both of these effects lead to an increase in Ecell. The polymer backbone, in addition to the functional groups, may also be susceptible to hydroxide attack particularly at the ether linkages found in some AEMs. Breakdown of the polymer backbone can cause the membrane to become thinner, decreasing ohmic resistance which leads to a decrease in Ecell and increase in hydrogen crossover. Because the different degradation processes can have opposing effects on Ecell, understanding the degradation mechanisms in AEMWEs solely from voltage behaviour is challenging. Electrochemical diagnostics alone are therefore insufficient for elucidating the causes of degradation processes. In this context, in-situ imaging techniques may enable the physical impacts of degradation, membrane thinning and catalyst detachment, to be observed. Operando imaging experiments take this idea further enabling degradation processes to be decoupled and correlated with changes in Ecell and impedance. X-ray computed tomography (X-ray CT) is a powerful technique for studying complex electrochemical systems as it enables the three-dimensional internal structure of cells to be observed non-destructively. X-ray CT has been used for in-situ and operando studies to gather information on membrane, catalyst layers, PTLs, interphases and transport phenomena, in various electrochemical devices such as fuel cells, electrolysers, and redox flow batteries. Operando X-ray CT studies have also been used to elucidate material degradation such as, membrane degradation, catalyst layer thinning and crack formations during accelerated stress tests in PEM fuel cells. In contrast, degradation-related operando studies on electrolyser devices are rather rare and often use ex-situ methods because operando imaging is still very challenging. In this study, we present the design and application of a miniature-electrolyser-cell (ME-cell) for use in X-ray microtomography (μ-CT). The electrochemical performance of the ME-cell was first validated and found to be comparable to a typical laboratory test fixture. We then investigated the degradation of catalyst-coated membranes (CCMs) fabricated with two different commercial AEMs (Fumasep® FAA-3-50 and Selemion™ AMVN ) using operando μ-CT. Results revealed significantly different behaviours between the two CCMs under constant current operation. The Fumasep® membrane displayed considerable thinning and conductivity loss, whereas the Selemion™ based CCM maintained its thickness and performance. Ultimately, the ME-cell introduced here provides a new platform for studying CCMs in a realistic electrolyser environment, by enabling the correlation of in-situ μ-CT images with electrochemical measurements.