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The physics of solid-state nanostructures is governed by the fact that materials properties change drastically when spatial dimensions are reaching the deBroglie wavelength of electrons. During the last decade, completely new functionalities have been achieved by exploiting these effects. On the other side, a comparable control in the fourth dimension, time, is still missing since it demands to manipulate optical transitions between quantum states on a few-femtosecond scale set by the oscillation period of light. This paper explores this fundamental regime of light-matter interaction. The experiments are based on recent advances of femtosecond technology such as ultrabroadband Ee:fiber lasers emitting single cycles of light, field-resolved detection of phase-locked electromagnetic transients with a bandwidth exceeding 100 THz and multi-terahertz sources delivering amplitudes in excess of 1 V/A which are comparable to inner-atomic fields. In this study on ultrafast nano-optics, a single semiconductor quantum dot was resonantly excited and coherently probed with a two-color femtosecond experiment. Full control over few-photon quantum statistics on molecular time scales is envisioned. To this end, the coupling between solid-state based few-level systems and the light field has to be maximized.