B) Whole mount immunofluorescence to stain cold stable microtubule fibers after in vivo maturation. Microtubules were stained with anti-tubulin antibody (green), centromeres with CREST serum (red) and DNA with Hoechst (blue). Bivalents are attached in a monopolar fashion. Approximate number of z-sections used for overlays to visualize the whole spindle (on the left) or individual chromosomes (magnifications on the right) are indicated.