In the virtual world, changing properties of objects such as their color, size or shape is one of the main means of communication. Objects are hidden or revealed when needed, or undergo changes in color or size to communicate importance. Users are in full control over how the virtual world looks and behaves. With augmented reality, virtual content is overlaid over the physical world to display information. Virtual reality enables users to completely dive into artificial environments. In the physical world, however, these features are not readily available. In this dissertation, we investigate how the dynamics of the virtual world can be brought into the real world. We are interested in modifying the optical properties of physical objects and devices to foster interaction and make the physical world more dynamic. To achieve this, we propose the concept of optically dynamic interfaces. Those interfaces change their appearance dynamically either through embedded capabilities or external augmentation. We describe the model of optically dynamic interfaces with three interconnected levels: dynamic objects, augmented objects and augmented surroundings. Dynamic objects are devices that integrate the capabilities to undergo visual changes. Augmented objects exhibit optically dynamic behavior through external augmentation. With augmented surroundings, objects that are unsuited for external augmentation due to their surface properties gain the ability the change their appearance. We present implementations of each of the levels and characterize their design spaces to gain insights into capabilities and limitations. Finally, we connect optically dynamic interfaces back to the virtual world with a new type of mixed reality, termed Remixed Reality. v I am in the lucky-and maybe unique-position of being able to thank not one but three advisors who guided my way throughout the process of this dissertation. Prof. Marc Alexa as my advisor at the Computer Graphics lab at TU Berlin. He helped me to foster the technical side of my research and kept me grounded when my ideas got a bit too crazy. Prof. Jörg Müller as my advisor during my time at the QU Lab at TU Berlin. He helped me shape the big picture of my research and continued to share his insights and feedback even after I left the lab. Prof. Michael Haller was my advisor during my studies in Hagenberg and during the first year of my doctoral studies. He introduced me to the field of HCI, and opened the gate to the world I am now part of. I would like to thank all of you for your continuing support and the way you shaped me as a researcher and as a person. Over the years I had the pleasure of working with many great people. Everything started at the Media Interaction Lab in Hagenberg. I would like to thank my colleagues and friends Kathrin Probst, Christian Rendl, Florian Perteneder, Jakob Leitner and Thomas Seifried for many interesting discussions and fruitful collaboration. I am grateful to Prof. Mark Hancock and Prof. Stacey Scott for their help during my time at the Univers...