With the necessity of finding alternative energy sources towards a greener world, new technical challenges are emerging. The improvement and development of existing or new materials is a requirement needed to implement these new alternatives energy sources. As hydrogen is believed to be a potential energy carrier, which can produce electricity with no emission of CO2, the interaction of hydrogen with the mentioned materials has to be understood, so that these can perform safely in such environments. The effect of hydrogen on materials has been studied for many years but the different experimental methodologies and results obtained lead to different interpretations and controversies. The main focus of this thesis was devoted to developing a novel experimental methodology to study hydrogen effects. A sophisticated novel approach, which combines in-situ hydrogen charging, tensile testing and high-resolution observation was developed. The method allows monitoring the deformation of any metallic sample without the risk of hydrogen outgassing. This is critical in materials with high hydrogen diffusivity that upon ex-situ hydrogen charging would lose the hydrogen once the test is started. The novel in-situ method was applied to study the effect of hydrogen on three materials: a nickel-based alloy, a complex phase steel and a tungsten-based alloy. The mechanical properties, fracture surface morphologies and crack propagation behavior were investigated with and without hydrogen, proving different hydrogen embrittlement susceptibility degrees for each material. Moreover, hydrogen concentration was calculated with a simple analytical model and with a more sophisticated simulation model. Finally, recently developed in-situ and in-operando methods were reviewed. All of these methods can be applied to study materials used in different hydrogen-related applications and should be considered in our pathway towards a green energy society.