Nano- and microelectrochemistry allows investigating electrocatalytic systems largely circumventing mass transport limitations. Hence, approaching smaller and smaller dimensions in electrochemistry is supposed to be beneficial for obtaining in-depth insight into electrocatalytic processes. This presentation includes (i) the reproducible fabrication of carbon-based nanoelectrodes, (ii) the development of enzyme-based nanoelectrodes for intra-cellular measurements, (iii) immobilization or growth of single nanoparticles on nanoelectrode surfaces, (iv) identical location TEM analysis of individual catalyst nanoparticles immobilized at nanoelectrodes, (iii) nanozymes as highly active electrocatalysts, to (iv) the characterization of novel catalyst materials for energy conversion.