Inspired by Brad Frost's talk about Atomic Design in 2013 at beyond tellerrand Christoph went back to trivago with the mission to completely change the way they deal with developing and designing the user interfaces for our products. From changing the mindset on how to approach Frontend Development and Design to refactoring our whole CSS codebase (know as Project Ironman) to introducing the first version of a Design System in 2015. In this talk Christoph shares learning, successes and failures during the introduction, roll-out and maintenance of the Design System. Christoph will touch on collaboration, fast changing environments, biases and technical requirements. A journey from ups and downs and the result of craving their own path and deprecating their Pattern Library while still having achieved the original mission to change the mindset around UI Engineering.