The peak statistic in weak lensing reconstructed mass maps is a new powerful tool to probe cosmology. Peaks trace the Universe large scale structures, but on the contrary to the two-point correlation function of the shear (aka cosmic shear), they are also sensitive to the non-linear regime of the growth of structures. In that sense they are similar to galaxy clusters. Although high peaks correspond to clusters, there is additional information contained in the low peaks arising from large scale structure projection effects.In this talk, I will introduce weak lensing peaks and compare them to cosmic shear and cluster abundance. I will apply shear peaks to the Kilo Degree Survey (KiDS), and discuss their cosmological constraints in light of the recent tension found between KiDS cosmic shear and Planck CMB. Finally, I will forecast the peaks cosmological constraints attainable with the Euclid survey, and compare them with the constraints expected from galaxy cluster counts.