The NLRP3 inflammasome is a key sensor for intracellular inflammation and a target for treating inflammation-related diseases. This study reveals the structural basis of NLRP3 activation, showing that it transitions from a closed cage to an activated disk-like inflammasome through oligomerization. Cryo-electron microscopy structures of NLRP3 in open and closed forms reveal that the NACHT domain undergoes a 90-degree hinge rotation, and mutations in the open octamer reduce IL-1β signaling, highlighting its role in activation. The centrosomal NIMA-related kinase 7 (NEK7) disrupts large NLRP3 oligomers, forming NEK7/NLRP3 monomers/dimers, a critical step in inflammasome assembly. These findings demonstrate that NLRP3 activation is cooperative and oligomerization is essential for inflammasome assembly. The study also shows that the open octamer forms through Back-Back, Head-Face, Tail-Tail, and Face-Face interactions, with the Face-Face interface playing a critical role in activation. Mutations at these interfaces reduce IL-1β signaling, but increased NLRP3 expression can overcome this effect. NEK7 dissociates NLRP3 oligomers into NEK7/NLRP3 dimers, which are essential for inflammasome assembly. The study provides insights into the structural and functional dynamics of NLRP3 activation and inflammasome assembly, highlighting the importance of oligomerization in this process. The findings have implications for understanding and treating inflammation-related diseases.The NLRP3 inflammasome is a key sensor for intracellular inflammation and a target for treating inflammation-related diseases. This study reveals the structural basis of NLRP3 activation, showing that it transitions from a closed cage to an activated disk-like inflammasome through oligomerization. Cryo-electron microscopy structures of NLRP3 in open and closed forms reveal that the NACHT domain undergoes a 90-degree hinge rotation, and mutations in the open octamer reduce IL-1β signaling, highlighting its role in activation. The centrosomal NIMA-related kinase 7 (NEK7) disrupts large NLRP3 oligomers, forming NEK7/NLRP3 monomers/dimers, a critical step in inflammasome assembly. These findings demonstrate that NLRP3 activation is cooperative and oligomerization is essential for inflammasome assembly. The study also shows that the open octamer forms through Back-Back, Head-Face, Tail-Tail, and Face-Face interactions, with the Face-Face interface playing a critical role in activation. Mutations at these interfaces reduce IL-1β signaling, but increased NLRP3 expression can overcome this effect. NEK7 dissociates NLRP3 oligomers into NEK7/NLRP3 dimers, which are essential for inflammasome assembly. The study provides insights into the structural and functional dynamics of NLRP3 activation and inflammasome assembly, highlighting the importance of oligomerization in this process. The findings have implications for understanding and treating inflammation-related diseases.