The assembly of a virus shell is like fastening a button: protein blocks must interlock in the correct order, and thermal fluctuations act like trembling fingers. With weak binding, the trembling helps find the right position — the shell closes faster. With strong binding, the fluctuations hinder: completing assembly is as tough as buttoning a button on stiff fabric with shaky hands.

Previously, this process was described like crystal growth, neglecting the 'trembling fingers.' But the edge trembling isn't just a nuisance: it's a tool: it increases entropy, the measure of disorder, and changes the edge tension. Amazingly, the amplitude of this trembling can reach the size of an entire protein block, as if a button were dancing in front of the buttonhole, tracing circles several centimeters wide. That's what controls the assembly speed.

The discovered mechanism explains the error-free assembly of viruses and hints at how to create nanocontainers for targeted drug delivery.