Orna Merchant learns how, during World War Two, a desperate Soviet Union created three all-female aerial combat units. The most celebrated of these was the 588th Night Bomber Regiment. Using Polikarpov Po-2 wooden biplanes, as the aviators approached their target they would cut their engines and glide in to drop their bombs. The eerie sight and sound of this – added to the discovery of them having all women crews - led German forces to nickname them ‘Nachthexen’ - the Night Witches.

How do humans cope with sadness? Is it something to be avoided at all costs or part of the human condition? Should we dwell on our sadness, or flee from it? Author Helen Russell explores humanity's history of gloom, and the cultural differences in our approach to tackling it. Helen goes to Lisbon to explore their relationship with melancholy, communicated through a uniquely mournful genre of music called Fado, and an untranslatable word "saudade". She learns about the service which sends a handsome man to wipe away tears in Japan, and hears about joy, sadness and mourning with a Ghanian poet.

Several countries are experiencing a fall in the number of babies being born and this has potentially serious consequences. Japan’s Prime Minister, Fumio Kishida, has warned that his country is on the brink of not being able to function as a society. The problem is an increasingly elderly population and not enough younger people to keep the country ticking over. China is seeing record low birth rates and South Korea has the lowest rate of women having babies in the world. Youtubers Sarah and Kyuho in the South Korean capital Seoul, describe some of the pressures and reactions they experienced when they said they are not planning to have kids.

Cuba and the United States share a long, complex history. From the Spanish-American War of 1898 to Fidel Castro's Cuba, these neighbours have often had an uneasy relationship. Claire Graham speaks with Ana Maria Roura, a BBC World Service journalist and Cuban native, to understand the history between the two nations.

Why did people take to the streets, risking arrest and a barrage of bullets? After protests turned violent and hundreds of people were killed, four Iranians tell the story of why they risked their lives. What has been happening in Iran to drive them out onto the streets to face bullets? ‘Agrin’ tells Phoebe Keane she’s tired of being objectified as a woman, and having no faith that the authorities will take sexual assault seriously when the police themselves are accused of raping prisoners. Mahsoud tells how he was shot during a protest but feared going to the hospital in case the authorities put him in jail. When plain clothed police loitered outside his family home, he decided to leave Iran. Still bleeding and with a metal pellet lodged in his ear impairing his hearing, he finally made it across the border to Iraq. ‘Nazy’ tells of being arrested by the morality police while walking to work and being shoved in a van as the heels on her shoes were too high. She started to protest every day and now walks through the streets with her hair blowing in the wind, an act of defiance. ‘Farah’ remembers a time in Iran when women could dance and sing in public and protests because she wants her daughter to live a life without fear. Presenter: Phoebe Keane Producers: Ed Butler, Ali Hamedani, Khosro Isfahani and Taraneh Stone Series editor: Penny Murphy