Single-molecule magnets, such as Mn12-acetate, are interesting to physicists primarily because quantum tunneling of the magnetization has been observed in this system. In addition, they may see applications in dense information storage or quantum computing. Mn12-acetate has spin S = 10, and the energy splitting between different spin orientations is on the order of meV, making time-domain THz spectroscopy a useful probe of the system. I will give an introduction to single-molecule magnets and show what THz spectroscopy has been able to teach us about them.