Preprofase

350px|right|thumb|Microtubule dynamics during preprophase and prophase in plant cell mitosis, modified from Donukshe et al. The images follow a Tobacco BY-2 cells|tobacco BY-2 cell through the first stages of mitosis (c. 12 minutes). The growing ends of microtubules are shown in green (labeled with [[green fluorescent protein fused to the microtubule plus end binding protein EB1 of Arabidopsis thaliana). N = Nucleus, V = Vacuole, PPB = Preprophase band, MTN = Microtubule nucleation starts at the nuclear envelope, NEB = Nuclear envelope breakdown at the onset of prometaphase. Also see the movie