“Periodical” is a new feature documentary from XTR and MSNBC Films that tells the unexpected story of the human body by exploring the marvel and mystery of the menstrual cycle. Though the most daring period scenes are being depicted in some programs, we still know alarmingly little when it comes to menstruation. The film shares stories from soccer champion Megan Rapinoe, who reveals how members of the U.S. Soccer Team track their cycles when training for the Women’s World Cup, to scientists discovering the possibilities of stem cells found in period blood, to young activists flipping the bill on period tax one state at a time, and much more and more. 1 hour, 33 minutes. Friday, Oct. 18, 4 pm. M.V. Film Center, Vineyard Haven. For tickets, visit mvfilmsociety.com.