Symfony Flex is a new way to compose Symfony applications, from Symfony 4 it's be default way to install any new applications, the idea behind it is to help on configuring and wiring the bundles into your applications by using recipes. Let's check how this works and which tricks are happening internally to make this magic happen, alongside with some new Symfony 3.4 and 4.0 features. Previous Symfony framework knowledge is desirable to follow this talk properly.