This chapter is dedicated to analysing how biological nuclear magnetic resonance (NMR) has evolved in the more than 70 years from its discovery and to discussing some of the applications of this technique to biological systems. To restrict a vast field, we treat liquid-state NMR leaving out solid-state applications that, although very important, are less consolidated and still fast evolving. We focus in particular on studies in complex environments, such as in-cell and/or crowded environments, that is a subject in which NMR can give its very best. We provide examples of various applications and hopefully show how versatile the technique is. We also briefly discuss how NMR can be coupled with other techniques to expand its horizons, increasing the intrinsic potentialities of this powerful technique.