During which stage of mitosis does chromatin condense into visible chromosomes?

During prophase, chromatin condenses into visible chromosomes, which is a critical step in mitosis. In this phase, the tightly coiled chromosomes can be seen under a light microscope as distinct entities. This condensation is essential because it allows the chromosomes to be moved efficiently during cell division without becoming entangled. Additionally, the nuclear envelope begins to break down during prophase, which facilitates the separation of the chromosomes that will occur in the subsequent phases of mitosis. This clear visibility of chromosomes is a defining characteristic of prophase and marks the transition from the interphase state, where DNA exists in a more loosely organized form as chromatin.