The detection of chemical explosives is crucial for military and civilian safety. A confluence of chemistry and engineering continues to improve the sensitivity for several classes of explosives, and holds the promise of cheap and portable sensing. Optical and fluorescence-based sensors have been extensively researched for portable applications due to their sensitivity and portability. This tutorial review discusses chemical approaches to sensing explosives based on an optical readout, and summarizes recent advances in fluorescence strategies, including fluorescence turn-on. It is of interest to researchers working in the areas of materials chemistry or forensics.