Final answer:
During the telophase stage of mitosis, chromosomes decondense and new nuclear envelopes form around each set of chromosomes, signaling the end of mitotic cell division.
Step-by-step explanation:
Unpacking of chromosomes and the formation of a new nuclear envelope is characteristic of the telophase stage of mitosis.
Telophase is the phase where chromosomes that have reached their respective poles begin to decondense and the previously disintegrated nuclear envelope re-forms around each set of separated chromosomes. This process signifies the nearing completion of mitotic cell division, transitioning eventually into cytokinesis, where the cell divides into two distinct daughter cells.