The cover picture shows a shock‐induced reaction in a porous bed of octahydro‐1,3,5,7‐tetranitro‐1,3,5,7‐tetrazocine (HMX). Our study shows compaction, reaction, and gas jetting during the initial stages of shock in the powder bed. Shock reflection at the glass window interface increases hot spot temperatures in HMX product gas in excess of 7000 K at higher impact speeds which is readily observable using pyrometry techniques. We extract a temperature histogram from simulations at discrete times, using it to calculate an effective emission spectrum and effective temperature, Teff, for comparison to data. Calculating Teff based on Planck's Law with a gray body assumption demonstrates good agreement with hot spot temperature data. The agreement with experimental results validates our mesoscale simulations as useful tools for elucidating the role of hot spot mechanisms in the shock initiation of heterogeneous explosives. More details can be found in the Full Paper by Harry Springer, Will Bassett, Sorin Bastea, Svjetlana Stekovic, and Craig Tarver on page 330 ff.