Final answer:
Dynamic instability is the process of microtubules growing and shrinking rapidly. When microtubules shrink it is called depolymerization, and when they grow it is called polymerization.
Step-by-step explanation:
Dynamic instability is the process by which microtubules grow and shrink rapidly. When microtubules shrink, it is called depolymerization.
This occurs when the subunits of the microtubules are disassembled. On the other hand, when microtubules grow, it is called polymerization. This occurs when new subunits are added to the microtubule structure.