Although the baryons in the intergalactic medium (IGM) trace dark matter fluctuations on megaparsec scales, on smaller scales ∼100 kpc, fluctuations are suppressed because the finite temperature gas is pressure supported against gravity, analogous to the classical Jeans argument. This Jeans filtering scale, which quantifies the small-scale structure of baryons in the IGM, provides a thermal record of heat injected by ultraviolet photons during cosmic reionization, as well as early X-ray pre-heating of the IGM, or other exotic heating mechanisms. Recently our group has shown that it is possible to directly measure the Jeans filtering scale of the intergalactic medium (IGM) by characterizing the coherence of correlated Ly-alpha forest absorption in close quasar pairs. Here I will interpret the first measurement of the Jeans filtering scale at 2<z<3 based on a unprecedented dataset of 90 close quasar pair spectra. I will discuss the cosmological implications of this measurement using hydrodynamical simulations coupled to models of reionization heating. Comparing these models to new measurements of the Jeans filtering scale provide an exciting new window for constraining heating events in the early Universe.