Greetings, podcast listeners! This week's Physics Central Podcast is a short story I heard about at the APS March Meeting that just wrapped up in Denver, Colorado. A physicist at Cornell University is studying bull sperm, and is looking at a phase transition that the sperm undergo. Basically, in a relaxed fluid, the sperm are disorganized: they all point in different directions. But when the flow of the fluid is turned up to a certain "critical flow rate" the sperm spontaneously point upstream. This type of order/disorder transition is a physics specialty: learn about the transition, look for commonalities with other systems that also undergo transitions, learn something new about bull sperm. Listen to the podcast to hear more!