Abstract: Ultracold atom technologies have transformed our ability to perform high-precision spectroscopy and apply it to time and frequency metrology.  Many of the highest-performing atomic clocks are based on laser-cooled atoms trapped in optical lattices.  These clocks can be applied to fundamental questions, for example to improve our understanding of gravity and general relativity.  In this talk, I will discuss using lattice-trapped ultracold diatomic molecules, rather than atoms, as a reference for clocks.  Molecules have more internal quantum states and therefore are relatively challenging to control.  On the other hand, their vibrational modes offer a large number of prospective clock transitions, and can help us probe alternative aspects of new physical interactions.  I will discuss the current precision limit of molecular metrology and possible paths forward.