The fleeting existence of pions inside of nuclei is responsible for the modification of nucleon properties in β decay μ-capture, photo-processes, magnetic moments and the like. The physical conditions of these virtual pions differ strongly from those of real pions, which can affect both their interactions and their behaviour inside of nuclei. These lectures discuss physical situations in which the interaction of the pions is expected to be very close to that of real pions, but in which the binding effects will manifest themselves fully. The purpose is to spotlight the essential physics of virtual pions. In the first lecture the effect of binding is illustrated by the line-shape of an absorbing (pionic) atom. The standard Breit-Wigner shape leads to logical inconsistencies of probability conservation far from the resonance energy. It is shown that a natural damping mechanism is introduced by the fact that the centre of the nucleus can only feel pions from a distance of the size of Yukawa field associated with the not quite real pion. In this situation, it is also possible to give a mathematically exact solution to the line-shape. In the second lecture a much more central problem is discussed, namely μ-capture at large energy transfers. In this situation μ-capture kinematically resembles π-capture. It is then useful to shift the normal viewpoint and consider the muon as surrounded by a cloud of pions, which will interact with the nucleus, when brought into contact with it: the muon becomes the source of the pion field and we see the strong interaction of the muon. In this way the muon is capable of mimicking all pionic effects. This only describes part of μ-capture. The remaining part can be studied via the leaking of the axial current by the pionic field (PCAC hypothesis). It is shown that when a natural locality hypothesis is introduced that the axial current can be determined completely in terms of the pions, in such a way that a very strong parallelism occurs between the e.m. induced polarization vectors in a dielectric, and the pionic polarization vector in the nuclear medium… Formulated in this fashion μ-capture can be uniquely determined as a pionic phenomenon at all momentum transfers: μ-capture becomes exactly equivalent to π-capture for virtual pions.