Every chemical research laboratory probably contains some form of explosion hazard. Clearly defining the molecular structure of energetic materials, especially those with trivial names, helps spot danger. Depiction of critical chemical functionality is useful for beginning preparative chemistry students and helpful in stimulating laboratory safety discussions. Here, common classes of hazardous substances (and physical explosions) are illustrated and briefly discussed: nitro, hydrazido, and azido groups, perchlorate ion, peroxides, and metal acetylides and fulminates. Emphasis is on conciseness involving clear examples of chemical structure and documentation of recent explosion incidents, where possible.