Surface plasmon polaritons can confine electromagnetic fields in subwavelength spaces and
are of interest for photonics, optical data storage devices and biosensing applications. In
analogy to photons, they exhibit wave–particle duality, whose different aspects have recently
been observed in separate tailored experiments. Here we demonstrate the ability of ultrafast
transmission electron microscopy to simultaneously image both the spatial interference and
the quantization of such confined plasmonic fields. Our experiments are accomplished by
spatiotemporally overlapping electron and light pulses on a single nanowire suspended on a
graphene film. The resulting energy exchange between single electrons and the quanta of the
photoinduced near-field is imaged synchronously with its spatial interference pattern. This
methodology enables the control and visualization of plasmonic fields at the nanoscale,
providing a promising tool for understanding the fundamental properties of confined
electromagnetic fields and the development of advanced photonic circuits.