  The problem of the origin of the elements is a fundamental one in astronomy
and one that has many open questions. Prominent examples include (1) the nature
of Type Ia supernovae and the timescale of their contributions; (2) the
observational identification of elements such as titanium and potassium with
the $\alpha$-elements in conflict with core-collapse supernova predictions; (3)
the number and relative importance of r-process sites; (4) the origin of carbon
and nitrogen and the influence of mixing and mass loss in winds; and (5) the
origin of the intermediate elements, such as Cu, Ge, As, and Se, that bridge
the region between charged-particle and neutron-capture reactions. The next
decade will bring to maturity many of the new tools that have recently made
their mark, such as large-scale chemical cartography of the Milky Way and its
satellites, the addition of astrometric and asteroseismic information, the
detection and characterization of gravitational wave events, 3-D simulations of
convection and model atmospheres, and improved laboratory measurements for
transition probabilities and nuclear masses. All of these areas are key for
continued improvement, and such improvement will benefit many areas of
astrophysics.
