The SOLID Harvard GSD series gathers material from the four Symposia on Architecture held at the Harvard University Graduate School of Design from 2014 to 2016, entitled All that is Solid. This issue, the third and final part of the series, offers a close reading of the interior in the context of contemporary architecture. It contains recent projects and relevant voices in support of the importance of the interior and the intimate material knowledge architects must demonstrate. With contributions from Richard Sennett, Kiel Moe, Salmaan Craig, and Iñaki Ábalos, it not only reflects the current complexity and the challenges faced by the discipline, but also traces future paths to explore.