Edvard Munch bequeathed his work to the city of Oslo so that it could be housed in a new museum. This is how Lambda’s story begins. This book explores the design and construction process of the building conceived by estudioHerreros that was opened to the public in October 2021. The title, Lambda Files, echoes the pseudonym that preserved the anonymity of the architects in the inter- national competition: unusually, the name was adopted by the public and the media to designate the project thereafter. The book takes a deep dive into the archives of estudioHerreros, bringing to light the “paperwork” materials that are usually disregarded by publications but which accurately document the professional, political, social, and technical context of the project. In the hands of its authors, the Munch project becomes an exploration of a number of present-day concerns, such as the importance of museums in rewriting history and imagining a desirable future, the need for dialogue as an instrument of design, environmental commitment, and the experimental responsibility of major projects.