We've entered the luteal phase and welcome a fascinating temporary organ into the reproductive system. It only lasts 14 days and it's one big job is to pump out progesterone. India also finds out what progesterone is doing to our brains and our bodies.

Credits: Presented by India Rakusen. Producer: Ellie Sans. Assistant Producer: Jorja McAndrew. Executive Producer: Suzy Grant. Original music composed and performed by Rebekah Reid. Sound Design by Charlie Brandon-King.

Special thanks to all contributors and audio diarists.

A Listen production for BBC Radio 4 and BBC Sounds.