Final answer:
During prophase, the first phase of mitosis, the cell undergoes various changes to prepare for division. The nuclear envelope breaks down, organelles fragment and disperse, the nucleolus disappears, centrosomes move to opposite poles, and microtubules form the mitotic spindle.
Step-by-step explanation:
During prophase, the first phase of mitosis, several events occur to prepare the cell for division. The nuclear envelope dissociates into small vesicles, and organelles such as the Golgi complex and endoplasmic reticulum fragment and disperse. The nucleolus disappears, centrosomes move to opposite poles, and microtubules form the mitotic spindle.