The advent of femtosecond light pulses has enabled the real-time visualization of dynamic processes at the nano- and molecular scale. Ultrafast transient absorption (TA) spectroscopy has provided an enormous amount of information on photoinduced dynamical processes in (bio)-molecules, nanostructures and solids1. Furthermore, these experiments have generally contributed to deepening our understanding of nonlinear light-matter interactions. In recent years. the ultrafast manipulation of light-matter interactions in photonic nano-architectures has unlocked unprecedented opportunities in the fi eld of nanophotonics, ranging from highspeed signal processing to the control of photophysical material functionalities. One of the most promising approaches to actively drive and dynamically reconfigure nanostructures at ultrafast speed, is indeed to use femtosecond optical pulses. In this context, I will discuss our contribution to design and experimentally demonstrate the control and the functionality of ultrafast metasurfaces (ultrathin planar sub-wavelength arrangements of resonant nano-antennas) in different scenarios [1-4]. First, I will show how ultrafast hot carrier spatial inhomogeneities at the nanoscale can manifest and even dominate the transient transmission of photonic metasurfaces. We theoretically predict and experimentally observe by femtosecond transient absorption spectroscopy that spatiotemporal dynamics of hot electrons can promote and control an ultrafast photoinduced anisotropy in plasmonic metasurfaces, enabling active reconfiguration of the nanostructure nonlinear response. Then, I will report on our observation of a giant all-optical modulations of dichroism in an anisotropic AlGaAs metasurface. Finally, I will introduce a new platform for controlling physico-chemical processes to tailor molecular dynamics on demand. By exploiting optical nanostructures, ultrashort laser light pulses and strong light-matter interactions, we aim at manipulating in real-time molecular reactions, with applications ranging from photovoltaics to photocatalysis.