  We demonstrate the formation of a single NaCs molecule in an optical tweezer
by magnetoassociation through an s-wave Feshbach resonance at 864.11(5)G.
Starting from single atoms cooled to their motional ground states, we achieve
conversion efficiencies of 47(1)%, and measure a molecular lifetime of
4.7(7)ms. By construction, the single molecules are predominantly (77(5)%) in
the center-of-mass motional ground state of the tweezer. Furthermore, we
produce a single p-wave molecule near 807G by first preparing one of the atoms
with one quantum of motional excitation. Our creation of a single weakly bound
molecule in a designated internal state in the motional ground state of an
optical tweezer is a crucial step towards coherent control of single molecules
in optical tweezer arrays.
