Metasurfaces are the subject of wide interest in the photonics community due to their flexibility in manipulating complex properties of light. These nanostructured arrays can simultaneously transform light’s polarization, phase, dispersion, momentum profiles and more. Such flexibility has already enabled the development in meta-optics of metalenses, dot projectors, polarimetry imaging, optical analogue processing, etc., which are now propelling us toward a new era of photonic technologies. However, future, more complex systems will be challenging to design, which will need to be overcome for further progress. In this talk, I will outline a general inverse-design strategy that I developed during my PhD to address this issue. I will present its capabilities in optimizing for highly efficient broadband polarizing metasurfaces and angle-tuneable metasurfaces. These ideas then lead to general optical image processing by carefully constructing a metasurface’s spatial frequency profile. I also address the issue of chromatic dispersion in gratings, and how metamaterials can not only overcome, but fully control that effect for our advantage. Lastly, I will extend the current inverse-design framework to the non-linear regime, where I demonstrate its full capability in optimizing devices that exhibit specific non-linear tensors and currents.