Prophase I continued.

• In Pachynema (Pachy: thick), the aligned homologous chromosomes (bivalents) continue to condense and 'zipper' together in a process called synapsis, forming tetrads which are held together by a synaptonemal complex. Non-sister chromatids may start exchanging genetic material in a process called crossing over.
  
  
• In Diplonema (Diplo: double), the homologues begin to separate, and chiasmata, regions where non-sister chromatids are intertwined and crossing over occurs, become visible.
  
  
  
  
  
• In Diakinesis (Dia: across), the chiasmata terminalize (move to the end of the tetrads). The homologues separate further, and centromeres attach the chromosomes to spindle fibers. The nucleolus and nuclear envelope break down.