Pachytene:

• The pairing of homologous chromosomes is completed.
• Chromosomes become more and more thick.
• Each bivalent has four chromatids, which wrap around each other.
• Non sister chromatids of homologous chromosomes exchange their segments due to Chiasmata formation, during the process called crossing over. In this way reshuffling of genetic material occurs which produce recombination.
• Pachytene may last for days and, weeks or even years, whereas leptontene and zygotene can last only for few hours.