The dependence of excited electron−hole state properties on the size of their host semiconducting nanostructures is the seed for a plethora of applications such as light-emitting diodes (LEDs) and photovoltaic cells. However, the inability of state-of-the art, diffractionlimited optical techniques to probe lifetime variations at the scale of individual quantum emitters precludes the full understanding of the nanostructures' optical properties. Here, we demonstrate the measurement of the individual lifetimes of quantum emitters a few angstroms thick separated by only a few nanometers, lifting the ambiguities usually faced by diffraction-limited techniques. This relies on the ability to monitor with subnanometer precision a fast electron beam that triggers extremely localized cathodoluminescence signals further analyzed through intensity interferometry (spatially resolved time-correlated cathodoluminescence, SRTC-CL). We demonstrate SRTC-CL to be a true nanometer counterpart of time-resolved photoluminescence, opening the way for a deeper understanding of suboptical wavelength objects such as biomarkers, quantum heterostructures, active parts of LEDs, or quantum optics devices. KEYWORDS: lifetime measurement, cathodoluminescence, STEM, intensity interferometry, time-resolved cathodoluminescence, III−V, quantum wells T he electron−hole (eh) excited-state deexcitation governs the optical properties of semiconductors. The physical properties of these eh states, specifically their emission energy and lifetime, depend on various parameters. These can be the size of the confining potential in the case of quantum wells (QW) or quantum dots (QDots), 1,2 the presence of an electrical field in the case of the quantum-confined Stark effect (QCSE) or spectral diffusion, 2,3 the type of defects in singlephoton emitters, or the presence of surface states in the vicinity of a particular emitter, to name a few. Whichever the parameters, a very small variation can lead to dramatic changes; see, for example, the atomic-scale dependence of GaN QDots or QW emission energy on their thickness. 4,5 Therefore, all applications, from LEDs to quantum optics or biomarkers, rely on the understanding and monitoring of structures that can be as small as an atom and separated by only a few nanometers. Characterization techniques providing lifetime measurements at the nanometer scale and furnishing structural and morphological information on the same object are thus required. An optical technique combining the performances of photoluminescence (PL) in terms of spectral and temporal resolutions and near-field techniques in terms of spatial resolution would be ideal. One of the main disadvantages of such a near-field time-resolved approach, as was quickly discovered, is that the very tip used for the near-field measurement influences strongly the value of the lifetime. 6 Such a near-field effect, at the heart of nano-optics, can be usefully exploited in many situations, such as for mapping the local density of electromagnetic states. 7 Another appr...