In mitosis, nucleolus and nuclear membrane disappear at

Prophase is the stage of mitosis in which the following events takes place like,
(i) The nucleolus disappears.
(ii) In the cytoplasm, the mitotic spindle, consisting of microtubules and other proteins, forms between the two pairs of centrioles as they migrate to opposite poles of the cell.
(iii) The nuclear envelope disappears at the end of prophase which indicates the beginning of the sub stage called prometaphase.
(iv) Chromosomes become more coiled and can be viewed under a light microscope.
(v) Each duplicated chromosome is seen as a pair of sister chromatids joined by the duplicated but unseparated centromere.