The phaseless coefficient inverse problem arises in imaging of nano-structures. One uses light source whose wavelength is in the range of hundreds of nanometers to illuminate those structures and collects the intensity of the complex scattering field on a plane behind such structures. Due to the smallness of the wavelength, measuring the phase of the scattering field is impossible. In this talk, we will establish an effective and stable method to reconstruct the lost phase. Then, the problem becomes the phased inverse scattering problem, which can be solved by the globally convergence method [Klibanov, Nguyen, Nguyen, Liu, 2017]. This is a joint work with M. Klibanov and D. L. Nguyen.