Older people are dreamers too. The Argentine Pope, leader of over a billion people, shakes hands with a girl from Sweden who has mobilised millions of young people (and many less young). Their shared dream is a world in which there is greater brotherhood and solidarity, where architects and engineers have forgotten how to design walls because now they are only asked to build bridges. They want a world in which all human activity - concerning the environment, economics, society, culture and daily life - is directed towards the common good of all people on earth and justice between generations. In a nutshell, they want a world in which "integral ecology" is applied, a key concept in Laudato Si', Pope Francis' encyclical letter "on care for our common home". Knowing that not everyone has the time to read papal documents or UN reports, Luca Fiorani takes us through the key concepts in Laudato Si', recent outcomes of international negotiations on climate change and the latest scientific data on the health of our planet.