Dielectric and metallic nanostructures can be tailored to provide unusual interaction with light waves. For example, they support localized resonances highly sensitive to the surroundings, complex scattering patterns and ultrafast nonlinearities. When arranged in 2D or 3D lattices, they form metasurfaces and metamaterials that enable to manipulate free-space light beams at will. However, the properties of such nanostructures also manifest when isolated, which could be used to advance in the miniaturization of photonic integrated circuits beyond the diffraction limit as well as to achieve new functionalities not attainable in conventional integrated optics. This could lead to the paradigm of hybrid plasmonicphotonic circuits consisting of subwavelength processing units linked by lossless dielectric waveguides. Here, I will show efficient ways to integrate dielectric and metallic nanostructures with silicon waveguides. The resulting structures could be useful in biosensing, Raman spectroscopy or ultrafast all-optical switching. In addition, I will show that when the nanostructure is placed asymmetrically with respect to the waveguide axis, it gives rise to spin-orbit interaction. This effect enables new functionalities such as polarization synthesis or Stokes nanopolarimetry, which can be implemented on a silicon chip in ultra-small foot-prints.