In the target-detected in-cell NMR only the target of interest is isotopically labeled (i.e., 15N labeled protein). For instance, target proteins can be isotopically labeled during cell growth in isotopically enriched (13C, 15N, or both 15N/13C) media [410]. The cell type and the labeling method may vary across experiments. Different cell types, including bacteria [411], oocytes [412], yeast cells [413], mammalian cells [414], HeLa cells [415] and even insect cells [416] have been reported in the literature. The fact that in-cell NMR applies to more than one cell type testifies of the versatility and potential application of this technique.