How do we determine the size of a macromolecule today? There are several methods but static and dynamic light scattering are among the most important ones. It is rather banal to say that we use the concept of photon there; the application of Einstein’s theory of motion is known at least by all graduate students. OK, but we want to know something more about the structure and dynamics of the large molecule although dynamic scattering already said a lot about it. We thus go two floors lower, into the laboratories of spectroscopy. This of course, as again everybody knows, is the domain of quantum mechanics - thus do we leave Einstein on the threshold? By no means: there are again photons here (one, two or more, depending on the rank of the spectroscopist) and spins as a bonus (those of nuclei in NMR, those of electrons two floors higher). Not everybody knows that a precise description of spin interaction cannot do without relativistic corrections and - behold - Einstein is with us again. With a short glance into future, the spin interactions probably will be the basis of future super-fast quantum computers - and you can bet (though not with a high stake) that an industrial quantum computer will use macromolecules.