Collective electron motion can unfold on attosecond time scales in nanoplasmonic systems, as defined by the inverse spectral bandwidth of the plasmonic resonant region. Similarly, in dielectrics or semiconductors, the laser-driven collective motion of electrons can occur on this characteristic time scale. Until now, such collective electron dynamics has not been directly observed on its natural, attosecond timescale. In ATTOCO, the attosecond, sub-cycle dynamics of strong-field driven collective electron dynamics in clusters and nanoparticles will be explored. Moreover, we will explore field-dependent processes induced by strong laser fields in nanometer sized matter, such as the metallization of dielectrics, which has been recently proposed theoretically.In order to map the collective electron motion we will apply the attosecond nanoplasmonic streaking technique, which has been proposed and developed theoretically. In this approach, the temporal resolution is achieved by limiting the emission of high energetic, direct photoelectrons to a sub-cycle time window using attosecond XUV pulses phase-locked to a driving few-cycle near-infrared field. Kinetic energy spectra of the photoelectrons recorded for different delays between the excitation field and the ionizing XUV pulse will allow extracting the spatio-temporal electron dynamics. ATTOCO offers the capability to measure field-induced material changes in real-time and to gain novel insight into collective electron dynamics. In particular, we aim to learn from ATTOCO in detail, how the collective electron motion is established, how the collective motion is driven by the strong external field and over which pathways and timescale the collective motion decays.ATTOCO provides also a major step in the development of lightwave (nano-)electronics, which may push the frontiers of electronics from multi-gigahertz to petahertz frequencies. If successfully accomplished, this development will herald the potential scalability of electron-based information technologies to lightwave frequencies, surpassing the speed of current computation and communication technology by many orders of magnitude.