Planar photonic crystals are dielectric nanostructures that are pursued worldwide as a platform for integrated nanophotonic circuits. Such circuits will process signals coded in light and will consist of thousands of basic components such as resonant nanocavities. At present, unavoidable nanometer-scale disorder makes such large-scale integration impossible. Disorder causes the resonances of the nanocavities to shift randomly, resulting in Anderson localization, an interference effect that blocks the propagation of light. Anderson localization – predicted in 1958 by Nobel Prize winner Philip Anderson – is an intriguing scientific phenomenon as well as a serious threat to applications.I propose to create adaptive nanophotonic systems. In these systems, I will use a spatially modulated light beam to modify the resonance frequency of each individual nanocavity. After adaptive tuning, the spatially structured light exactly counteracts the disorder and guides signals safely through the nanophotonic circuit. Effectively the signals will propagate in a perfect nanophotonic structure. As a second main innovation, I will employ an ultrafast structured light beam to write new, ordered and functional patterns into the circuit. This transformational technology will enable applications wherein optical circuits become fully programmable. The circuit will be modified dynamically in less time than that needed for a photon to pass through it. Spatial light modulators will enable us to address and control thousands of individual nanophotonic components.Our dynamic and adaptive nanophotonic system will enable new technology, such as dynamically tunable delay lines, and open up new regimes of light propagation: the crossover regime of Anderson localization, ultraslow light that propagates scarcely faster than sound, and dynamic light propagation where the time dependence of the nanostructure drastically influences the flow of light.