For more than 65 years, scientists have been fascinated by the idea to miniaturize electrical circuits toward the smallest length scales. One particular way is inspired by nature itself,... Show moreFor more than 65 years, scientists have been fascinated by the idea to miniaturize electrical circuits toward the smallest length scales. One particular way is inspired by nature itself, specifically to assemble electrical components and switches from atoms and molecules. The molecules typically used have dimensions of the scale of a few nanometers (1 nanometer = 0,000000001 meter). The scientific research area that represents the study of electrical currents through molecules is called "molecular charge transport" or "molecular electronics". In this thesis, I have performed fundamental research on charge transport through various molecules. Specifically, I have investigated a special type of molecule that has the ability to change its spin state. To test these functional molecules, I have used a more robust type of molecular device that enables me to bridge the size gap mentioned above. This thesis has led to two important new insights. First, the properties of a switchable molecular device can be strongly enhanced artificially by making use of a charge transport mechanism called multiple inelastic cotunneling. Second, we show that the spin transition phenomenon can take place in a molecular-nanoparticle ensemble. Show less