A cell cycle process comprising the steps by which a cell progresses through prometaphase, the stage following prophase in mitosis (in higher eukaryotes) during which the nuclear envelope is disrupted and breaks into membrane vesicles, and the spindle microtubules enter the nuclear region. Kinetochores mature on each centromere and attach to some of the spindle microtubules. Kinetochore microtubules begin the process of aligning chromosomes in one plane halfway between the poles.