Most of the recent applications of solid-state NMR to biological science have focused on the determination of the total structure of a peptide or protein in a micro-crystal, or a reconstituted model membrane, or a precipitated amyloid fibril or plaque.  These applications have successfully adapted many of the popular multi-dimensional solution-state NMR experiments to the special demands of the solid state for samples that are either mechanically spun or aligned.  For the last 30 years, our laboratory has been engaged in an effort to use solid-state NMR to detect (with a minimum of perturbation) stable isotope labels that have been introduced in vivo in bacteria, plants, insects, and shellfish.  The goal is obviously not to determine a total structure but rather to connect partial local structure with biological function.  We illustrate this strategy with an example: a correlation between photorespiration and glycine metabolism in intact leaves of Glycine max (soybeans).  In this example, the principal NMR tool is rotational-echo double resonance (REDOR), whose use is illustrated in the figure.