The mapping of single cell mechanics in embryos and tissues is essential to characterise their morphogenesis, and to investigate their genetic control and coupling to the underlying biochemical signalling. To date, most direct cell mechanics measurements are either invasive (laser ablation) or do not allow to map forces in the whole 3D tissue or embryo. Alternatively, the shape of cells and their spatial arrangement being the direct result of the cellular forces at play, they constitute the direct expression of the underlying mechanical force balance. Here, I will introduce an inverse approach and computational framework to infer relative interfacial tensions and cell pressures directly from 3D microscopy images of cell contours. I will present the validation of the method on realistic confocal artificial images of simulated embryos, and discuss its robustness to noise in the images and underlying shapes. I will then show applications to several experimental confocal microscopy images of embryos, including mouse, ascidian and C. elegans species, revealing interesting new insights into their cell mechanical regulation. I will finally discuss limitations of the method and future perspectives.