Non-invasive microscopy exploits light scattering to obtain a three-dimensional image of biological tissues. However, light propagation is drastically affected by the heterogeneities of tissues, which totally blurs microscopic images in depth. Adapted from astronomy, adaptive optics has been developed to compensate for these aberrations in microscopy, but the associated frame rate and penetration depth remain extremely limited for 3D imaging. We have therefore developed a revolutionary microscope that can acquire three-dimensional images of tissue at millimetric depths, with sub-cellular resolution (250 nm) and high frame rates (1 to 200 Hz). This paradigm shift is based on ultra-fast acquisition of the reflection matrix using sparse sample illumination and interferometric measurement of reflected light at multiple wavelengths [1]. The light focusing process is optimized in post-processing for any voxel in the medium, using smart algorithms to overcome the problems of aberrations and multiple scattering that have hitherto impaired the performance of conventional microscopes [2].  This work paves the way for a fully digital microscope enabling quantitative, in-depth in-vivo tissue inspection in real time. Applications range from the control of embryos in the in-vitro fertilization process to the control of organoids for biomedical applications, ophthalmology (high-resolution imaging of the cornea and ultra-deep imaging of the retina) and dermatology (in-depth control of melanomas).