Media Informatics professionals that work on the user interface of interactive products, systems and services need to communicate their design ideas efficiently to team members from a variety of other professions. Moreover, capturing the user interface design lessons learned from a completed project is crucial to avoid repeating costly earlier mistakes. After this class, students will be able to write clear and cross-disciplinary design patterns that each captures the essence of a certain user interface design decision and its tradeoffs. They will be able to combine these patterns into larger structures called pattern languages, and will also be able to utilize existing pattern languages on the market to quickly learn about crucial design guidelines for specific interface markets, such as web sites or mobile devices, for example.This lecture will cover the current research topic of design patterns in the area of interactive system design and user interface development. We will see how design patterns originated in architecture, were first adopted by software engineering, and then found their way to HCI where they have proven to be an exciting new suitable format to express design guidelines in a semi-formalized and reusable way.