The period when a cell is not dividing is called [blank_start]interphase[blank_end]. The stage of mitosis when the chromosomes are first visible as distinct structures is called [blank_start]prophase[blank_end]. During this stage thin threads develop that span the cell from end to end and together form a structure called the [blank_start]spindle apparatus[blank_end]. Towards the end of this stage, the [blank_start]nuclear envelope[blank_end] breaks down and the [blank_start]nucleolus[blank_end] disappears. The stage when the chromosomes arrange themselves across the centre of the cell is called [blank_start]metaphase[blank_end]. During the stage called [blank_start]anaphase[blank_end] the chromatids move to opposite ends of the cell.