In the last decade, the fields of nanoplasmonics and photonic crystals have opened up the nanoscale for optical control. Both the flow and emission of light can be controlled at these small length scales, giving rise to new science and applications. Interestingly, freely propagating light beams can already contain nanoscale features, i.e. optical singularities. Little is known about this nanoscale structure of light.I propose to (1) reveal the structure of light at the nanoscale and its interaction with geometrical structures or other light structures; and (2) achieve full spatio-temporal control of the nanoscale structure of light. Crucial to achieving these goals are technological innovations, which will be crosscutting objectives. These include the first nonlinear vectorial scanning near-field microscope and novel near-field probes allowing access to new combinations of vector fields.This next step in the field of nano-optics is possible due to recent breakthroughs in the control and visualization of light at the nanoscale obtained in my group. I will combine newly acquired access to the vectorial nature of light with its active control to investigate how (deep-) subwavelength structures of light of different frequencies affect each other when coupled through a nonlinear interaction in a nanostructured material. In parallel I will focus on optical singularities. Because of their extreme size, small changes in their position will lead to huge effects in the local light fields, opening up potential for all-optical and therefore ultrafast control.The research will lead to innovations in the visualization and control of light at the nanoscale, access to the magnetic component of light, nanoscale nonlinear optics and coherent control of light fields. The knowledge gain will be crucial for applications like ultrasensitive biosensors based on superchiral light, ultrafast magneto-optics and nanoscale quantum optics.