Carlos Umaña (Costa Rica) won the Nobel Peace Prize in 2017 together with the International Campaign to Abolish Nuclear Weapons (ICAN) for calling attention “to the catastrophic humanitarian consequences of any use of nuclear weapons” and for their “ground-breaking efforts to achieve a treaty-based prohibition of such weapons”. He comes to Queretaro, in the country of the Tlatelolco Treaty, to talk about environmentalism, the need to eradicate nuclear arsenals from the world and what it is like to combine work as a scientist and an activist. In conversation with Elisa Guerra.