  Observation of the quantum anomalous Hall effect (QAHE) in MnBi$_2$Te$_4$
flakes is one of the most exciting results in the study of the intrinsic
magnetic topological insulator MnBi$_2$Te$_4$ and related compounds. This
fascinating result is yet to be reproduced two years after its first report.
The quality of starting MnBi$_2$Te$_4$ single crystals is believed to be the
key factor. An interesting and important question to address is what is the
right quality to enable the QAHE. In this perspective, we present possible
approaches to tuning the magnetic and topological properties of MnBi$_2$Te$_4$
by using lattice imperfections, strain, stacking sequence, and interactions
between the substrate and flakes/films. It is of critical importance to
eventually identify the factor(s) responsible for the realization of QAHE.
