  We create molecules from fermionic atoms in a three-dimensional optical
lattice using a Feshbach resonance. In the limit of low tunnelling, the
individual wells can be regarded as independent three-dimensional harmonic
oscillators. The measured binding energies for varying scattering length agree
excellently with the theoretical prediction for two interacting atoms in a
harmonic oscillator. We demonstrate that the formation of molecules can be used
to measure the occupancy of the lattice and perform thermometry.
