We're very excited to be going to this year's European Congress of Mathematics (ECM), which will take place in Seville, Spain, in July! We noticed that mathematicians who win one of the prizes awarded at the ECM by the European Mathematical Society quite often go on to win a Fields Medal, one of the highest honours in mathematics. So to celebrate the run-up to the ECM we've launched Euromaths, a miniseries of podcasts revisiting interviews with Fields Medallists who previously won an EMS prize. This week we hear from Maryna Viazovska who won a Fields Medal in 2022 and an EMS prize in 2020, talking about the theory of optimal transport and how it applies to a wide range of things, from crystals to clouds. You can read about Maryna's work in this article. To listen to previous episodes of Euromaths click here. This content was originally produced as part of our collaborations with the London Mathematical Society and the Isaac Newton Institute for Mathematical Sciences. You can find all our content on the 2022 International Congress of Mathematicians here.