* Chromosomes: The most dramatic events of mitosis involve the chromosomes, which reside in the nucleus. These chromosomes are duplicated and then meticulously separated into two identical sets.
* Nuclear Envelope: The nuclear envelope breaks down at the beginning of mitosis to allow the chromosomes to access the cytoplasm. It then reforms around the separated chromosomes, creating two new nuclei.
* Spindle Fibers: While microtubules (which form spindle fibers) originate from the centrosomes outside the nucleus, they extend into the nucleus to attach to the chromosomes. They are crucial for pulling the chromosomes apart.
While the cytoplasm is also involved (especially in the formation of the spindle fibers), the nucleus is the central stage for the most critical events of mitosis: chromosome duplication and segregation.
