Is it possible to really ‘see’ how fast electrons flow in nanoscale optoelectronic circuits? Can we, in this way, get a complete understanding of the real-time dynamics of electrons in nanoscale circuits?The vision of this ERC proposal is to establish a research area at the interface of condensed matter physics, ultrafast optics, and electrical engineering which has so far been nearly completely unexplored: the investigation of real-time dynamics of photoexcited charge carriers in electrically contacted nanosystems with the highest precision possible. By doing so, unique information about the optoelectronic processes in nanoscale circuits shall be obtained. Four interconnected visions are pursued all with applications in information technology and electrical engineering. The approach is risky, however, it promises very interesting physics on the way. We will: (i) explore the fastest and smallest photoswitches fully integrated in electric circuits, (ii) probe single and collective charge excitations for the fastest nanoscale optoelectronic devices, (iii) determine the radiative and non-radiative lifetimes in photovoltaic circuits time-resolved, (iv) discover how fast nanoscale photo-thermoelectric devices operate. Towards these visions, I propose to use a real-time optoelectronic ‘on-chip’ detection scheme for nanoscale circuits, which was developed by us very recently. In this setup, I intend to carry out time-of-flight experiments of photoexcited electrons in nanoscale circuits, to investigate the ultimate switching speed of optoelectronic devices, and to explore the ultrafast dynamics of photothermo-electric currents in electrically contacted nanosystems.The project gives essential insights for designing and implementing nanoscale circuits into optoelectronic switches, photodetectors, solar cells, thermo-electric devices as well as high-speed off-chip/on-chip communication modules to make ultrafast nanoscale optoelectronics real.