Researchers at Stockholm University employed cryo-electron microscopy to reveal the molecular architecture of the complete 14-subunit botulinum neurotoxin type B1 complex. This toxin, the most potent known biological toxin, operates within a large protein complex shielding it from degradation and facilitating crossing of gut epithelial barriers. The study elucidated the assembly, protective mechanisms, and pH-dependent release processes of the toxin complex. This structural insight paves the way for designing more effective therapeutics and improving safety of clinical applications involving botulinum toxins.