Single-molecule spectroscopy allows the direct observation of conformational dynamics in individual biomolecules. Here, we describe how single-molecule Förster resonance energy transfer (smFRET) reveals heterogeneous kinetics in the EBS1*/IBS1* interaction, two RNA sequences that play an important role in group II intron mediated self-cleavage. Further examples of dynamic heterogeneity in functional nucleic acids are provided and the possible origins of this phenomenon are discussed.