  Na3Bi was the first experimentally verified topological Dirac semimetal
(TDS), and is a 3D analogue of graphene hosting relativistic Dirac fermions.
Its unconventional momentum-energy relationship is interesting from a
fundamental perspective, yielding exciting physical properties such as chiral
charge carriers, the chiral anomaly, and weak anti-localization. It also shows
promise for realising topological electronic devices such as topological
transistors.
  In this review, an overview of the substantial progress achieved in the last
few years on Na3Bi is presented, with a focus on technologically relevant
large-area thin films synthesised via molecular beam epitaxy. Key theoretical
aspects underpinning the unique electronic properties of Na3Bi are introduced.
Next, the growth process on different substrates is reviewed. Spectroscopic and
microscopic features are illustrated, and an analysis of semi-classical and
quantum transport phenomena in different doping regimes is provided. The
emergent properties arising from confinement in two dimensions, including
thickness-dependent and electric-field driven topological phase transitions,
are addressed, with an outlook towards current challenges and expected future
progress.
