The miniaturisation of devices has become of paramount importance in modern technology in the last century. Since then, the lower bound of the nanotech world has been pushed down until the molecular and atomic scale. At these dimensions, classic and quantum processes coexist both for magnetic and electric phenomena. This is creating a physical limit for modern silicon-based technologies based on classic transport. Molecular spintronics is one of the most promising approaches to overcome these limits. This field relies on the exploitation of single-molecules magnets, the smallest possible molecular magnets that can be created. Not only it allows for the ultimate electrical miniaturisation to the molecular scale, but it also has the potential to unlock the power of quantum computation. However, the electric transport properties and the magnetic interaction with the environment at this scale require more investigation. The present work focuses on the charge transport in molecular magnetic materials through different dimensionalities. We begin the journey by analysing microscopic crystals of nitronyl-nitroxide radicals, getting an insight on their conduction channels through space-charge-limited currents. We then scale down one dimension, and analyse thin-film devices based on rare-earth single-molecule magnets, to verify their behaviour when deposited on surfaces. Finally, we embed graphene nanoribbons and rare-earth single-molecule magnets in graphene break junctions, unravelling their magnetic properties as single-molecule transistor.