Recent progress in atomic-resolution spin-polarized scanning tunneling microscopy (SP-STM) and spectroscopy (SP-STS) performed in external magnetic fields has led to a novel method of magnetometry at the single-atom level. Based on measurements of single-atom magnetization curves, magnetic interactions between individual atoms on surfaces can now be revealed in real space. Moreover, spin-selective imaging of orbital states of individual atoms has recently been achieved by SP-STM. The combination of STM-based single-atom manipulation techniques and single-atom magnetometry by SP-STM allows unprecedented insight into the magnetic properties of artificially created nanostructures. (C) 2010 Elsevier Ltd. All rights reserved.