In general, biological macromolecules require significant dynamical freedom to carry out their different functions, includingsignal transduction, metabolism, catalysis and gene regulation. Effectors (ligands, DNA and external milieu, etc) areconsidered to function in a purely dynamical manner by selectively stabilizing a specific dynamical state, thereby regulatingbiological function. In particular, proteins in presence of these effectors can exist in several dynamical states with distinctbinding or enzymatic activity. Here, we have reviewed the efficacy of ultrafast fluorescence spectroscopy to monitor thedynamical flexibility of various proteins in presence of different effectors leading to their biological activity. Recent studiesdemonstrate the potency of a combined approach involving picosecond-resolved Fo¨ rster resonance energy transfer,polarisation-gated fluorescence and time-dependent stokes shift for the exploration of ultrafast dynamics in biomolecularrecognition of various protein molecules. The allosteric protein–protein recognition following differential protein–DNAinteraction is shown to be a consequence of some ultrafast segmental motions at the C-terminal of Gal repressor proteindimer with DNA operator sequences OE and OI. Differential ultrafast dynamics at the C-terminal of k-repressor protein withtwo different operator DNA sequences for the protein–protein interaction with different strengths is also reviewed. We havealso systemically briefed the study on the role of ultrafast dynamics of water molecules on the functionality of enzymeproteins a-chymotrypsin and deoxyribonuclease I. The studies on the essential ultrafast dynamics at the active site of theenzyme a-chymotrypsin by using an anthraniloyl fluorescent extrinsic probe covalently attached to the serine-195 residuefor the enzymatic activity at homeothermic condition has also been reviewed. Finally, we have highlighted the evidence thata photoinduced dynamical event dictates the molecular recognition of a photochromic ligand, dihydroindolizine with theserine protease a-chymotrypsin and with a liposome (L-a-phosphatidylcholine).