Scanning probe microscopies (SPM), and in particular Scanning Tunneling Microscopy (STM) and Atomic Force Microscopy (AFM), allow high resolution imaging in the direct space of surfaces and represent thus an essential tool for the investigation of surfaces and supported nanostructures down to the nanometer and atomic scale. After a brief historical introduction, the lecture provides an overview of the basic principles of STM and AFM, and a description of the experimental setups required for STM and AFM measurements. It will also be shown that measurement of surface electronic properties (i.e. of the surface LDOS, Local electron Density of States) is possible by means of Scanning Tunneling Spectroscopy (STS). Examples drawn from the fields of surface science and bio-nanotechnologies will be illustrated, ranging from the study of nanostructured thin films and clusters deposited on surfaces to the imaging of proteins and biomolecules.