FN1 and breast cancer: Leveraging a peptide probe capable of detecting fibronectin fiber tension‐as fiber stretching destroys its multivalent binding motive‐ our recent work has demonstrated that fibronectin fibers are highly tensed in healthy organs, but lose their tension in pathological ECM, as shown in both murine cancer and fibrosis models, as well as in human breast cancer.[56, 65, 67, 68, 91] Given that the brain is the softest organ in the human body,[35, 92] we specifically examined the remodeling of fibronectin fibers and how their tension might get altered in human glioblastoma cryosections.