***Imaging tissue fibrosis** (a) Mid-infrared dichroism-sensitive photoacoustic microscopy (MIR-DS-PAM) images of cell-induced fibrosis (CIF) and normal control (NC) tissue; (c) MIR-DS-PAM images of drug-induced fibrosis (DIF) and NC tissue; (b) and (d) show the corresponding confocal fluorescence microscopy (CFM) images. Scale bars: 500 µm. (Courtesy: CC-BY 4.0/Light Sci. Appl.* 10.1038/s41377-025-02117-0) Many of the tissues in the human body rely upon highly organized microstructures to function effectively. If the collagen fibres in heart muscle become disordered, for instance, this can lead to or reflect disorders such as fibrosis and cancer. To image and analyse such structural changes, researchers at Pohang University of Science and Technology (POSTECH) in Korea have developed a new label-free microscopy technique and demonstrated its use in engineered heart tissue.…