The Ho group follows the long tradition of developing new instrumentation and methods for precision measurements of atoms and molecules adsorbed on solid surfaces. Over the last 25 years, the group has used homemade cryogenic scanning tunneling microscopes (STM) in ultrahigh vacuum to advance the field of single molecule chemistry, physics, and optics. In 1998, the group discovered spatially resolved inelastic electron tunneling (IET) to enable spectroscopy and microscopy with the STM of quantum excitations at the atomic scale, particularly involving vibration and spin states. In addition, IET drove a wide range of single-molecule motions, particularly vibration initiated energy transfer processes, structural transformation, and bond dissociation. Previously unknown molecular properties were discovered, including vibration induced negative differential resistance, Zeeman splitting without unpaired electrons, coupled spin-vibration states, and giant rectification current enabled by quantum excitations. IET enabled the achievement of diffraction unlimited Ångstrӧm spatial resolution in optical phenomena and the development of the inelastic tunneling probe as new quantum sensors based on attaching a single molecule to the STM tip to reach the ultimate precision and spatial resolution of electrostatic and magnetic sensing. By combining near-IR optical femtosecond lasers with STM, measurement of single molecule dynamics with joint Å-fs space-time resolution was realized. Most recently, the research focuses on probing single molecules with IR and femtosecond and continuous wave terahertz lasers coupled with STM. A singular objective lies in the exploration of the quantum coherence of qubits based on magnetic atoms and molecules containing transition metal and rare earth elements to advance the nascent field of quantum information science.