Sixty years ago in December 1959, when Richard Feynman said that there is "Plenty of Room at the Bottom", he envisioned the seemingly endless possibilities of the microscopic world, which we now refer to as Nanoscience. However, his statement also implies that there is a bottom meaning that there is a limit to the miniaturization of every process. I will discuss the fundamental limits of transport in scanning tunneling microscopy. This concerns, for example, the changes in the tunneling process imposed by revealing the quantum nature of the electron charge at extremely low temperatures. Further, we exploit magnetic impurities coupled to a superconductor to create single quasiparticle levels inside the superconducting gap (Yu-Shiba-Rusinov states). I will show how we use these states to demonstrate the bare minimum of what is necessary to create a tunneling current.