  Relativistic quantum chemistry has evolved into a fertile and large field and
is now becoming an integrated part of mainstream chemistry. Yet, given the
much-involved physics and mathematics (as compared with nonrelativistic quantum
chemistry), it is still necessary to clean up the essentials underlying the
relativistic electronic structure theories and methodologies (such that
uninitiated readers can pick up quickly the right ideas and tools for further
development or application) and meanwhile pinpoint future directions of the
field. To this end, the three aspects of electronic structure calculations,
i.e., relativity, correlation, and QED, will be highlighted.
