During which stage of mitosis do the chromatids condense and the nuclear envelope break down?

During prophase, the chromatids undergo significant condensation, becoming more compact and visible under a microscope. This is a critical stage as it allows the chromatin, which is the loose form of genetic material present during interphase, to organize into distinct chromosomes. Additionally, during prophase, the nuclear envelope starts to disintegrate, leading to the release of chromosomes into the cytoplasm. This breakdown of the nuclear envelope is essential for the subsequent stages of mitosis, allowing the spindle fibers to access the chromosomes and ensuring their correct alignment and separation in later phases.

The actions occurring during prophase set the stage for the orderly distribution of genetic material to the daughter cells, making this stage vital for successful cell division.