Probing Ultrafast Chemical Dynamics Inspired by the Rhythms of Fireflies Coherence phenomena arise from interference, or the addition, of wave -like amplitudes in phase  . While coherence has been shown to yield transformative new ways for improving function, advances have been limited to pristine matter, as quantum coherence is considered fragile. Here I will discuss how vibrational an d vibronic wavepackets entrain ensembles of molecules, like the synchronized flashing of fireflies . I will discuss how this can be used to probe mechanisms of ultrafast dynamics and how in -step vibrational motion might be employed to control function on ul trafast timescales. I will give examples that include light -harvesting in photosynthesis, energy flow in organometallic molecules that is ‘wired’ by Fermi resonance, and ultrafast electron transfer in molecular systems.  Scholes, et al. “Optimal Coherence in Chemical and Biophysical Dynamics” Nature 543, 647 – 656 (2017) .