  Next-generation concepts for solid-state memory devices are based on
current-driven domain wall propagation, where the wall velocity governs the
device performance. It has been shown that the domain wall velocity and the
direction of travel is controlled by the nature of the wall and its chirality.
This chirality is attributed to effects emerging from the lack of inversion
symmetry at the interface between a ferromagnet and a heavy metal, leading to
an interfacial Dzyaloshinskii-Moriya interaction that can control the shape and
chirality of the magnetic domain wall. Here we present direct imaging of domain
walls in Pt/Co/AlO$_x$ films using Lorentz transmission electron microscopy,
demonstrating the presence of homochiral, and thus topologically protected,
N\'{e}el walls. Such domain walls are good candidates for dense data storage,
bringing the bit size down close to the limit of the domain wall width.
