Research on molecule-based-nanomagnets has progressed rapidly in recent years in materials known as single molecule magnets (SMMs), which exhibit a host of remarkable quantum phenomena. SMMs represent a molecular or 'bottom-up' approach to nanomagnetism, with advantages that include chemical control of molecular structure, spin, magnetic anisotropy as well as intra- and intermolecular magnetic interactions. They display properties of much larger ferromagnetic particles prepared by conventional lithographic methods but in a manner that enables fundamental physics studies. For example, quantum tunneling of the magnetization and quantum phase interference have been clearly demonstrated and studied experimentally in these materials. In this talk I will present an overview of this field, highlighting key experimental and theoretical developments. I will also present recent studies in my group that employ magnetization measurements and microwave spectroscopy to characterize superpositions states of up and down high spin-projections that are at the heart of the quantum tunneling phenomena.