Discusses research being done on the role of GTPase Ran in mitotic spindle assembly. Reference to the studies by R.E. Carazo-Salas et al, A. Wilde et al, O.J. Gruss et al, M.V. Nanchury et al and C. Wiese et al; Factors regulated by GTPase Ran; Description and function of importin-β sequesters; Factor involved in spindle assembly.