An MIT engineering team has unveiled the critical influence of intercellular fluid—the watery medium occupying spaces between cells—on tissue flexibility and mechanical response under deformation. Published in Nature Physics, their research challenges the exclusive focus on intracellular components, demonstrating that ease of fluid flow within these spaces governs tissue compliance and relaxation. This insight broadens understanding of tissue behaviors related to aging, disease progression, and recovery processes, highlighting extracellular fluid dynamics as a novel target for therapeutic modulation.