Deep tissue chemical imaging has a vital role in biological and medical applications. Current approaches suffer from water absorption and tissue scattering, which limits imaging depth to hundreds of micrometres. The shortwave infrared spectral window allows deep tissue imaging but typically features unsatisfactory spatial resolution or low detection sensitivity. Here we present a shortwave infrared photothermal (SWIP) microscope for millimetre-deep vibrational imaging with micrometre lateral resolution. By pumping the overtone transition of carbon–hydrogen bonds and probing the subsequent photothermal lens with shortwave infrared light, SWIP can obtain chemical contrast from 1 μm polymer particles located at 800 μm depth in a highly scattering phantom. The amplitude of the SWIP signal is shown to be 63 times larger than that of the optically probed photoacoustic signal. We further demonstrate that SWIP can resolve intracellular lipids across an intact tumour spheroid and the layered structure in thick liver, skin, brain and breast tissues. SWIP microscopy fills a gap in vibrational imaging with subcellular resolution and millimetre-level penetration, which heralds broad potential for life science and clinical applications.

深层组织化学成像在生物和医学应用中具有至关重要的作用。目前的方法受到水吸收和组织散射的影响，这将成像深度限制在数百微米。短波红外光谱窗口允许深层组织成像，但通常具有空间分辨率不令人满意或检测灵敏度低的特点。在这里，我们提出了一种短波红外光热 (SWIP) 显微镜，用于具有微米横向分辨率的毫米深振动成像。通过泵浦碳氢键的泛音跃迁并用短波红外光探测随后的光热透镜，SWIP 可以从高度散射体模中位于 800μm 深度的 1μm 聚合物颗粒获得化学对比度。 SWIP 信号的幅度比光学探测的光声信号的幅度大 63 倍。我们进一步证明，SWIP 可以解析完整肿瘤球体以及厚肝脏、皮肤、大脑和乳腺组织中的层状结构的细胞内脂质。 SWIP 显微镜填补了振动成像领域的亚细胞分辨率和毫米级穿透力的空白，这预示着生命科学和临床应用的广阔潜力。