An overview on vacuum and thermal fluctuations of the electromagnetic field in empty space at a few nanometer distance from solid structures is given. The material properties of the structures are described macroscopically in terms of electric and magnetic susceptibilities. The field fluctuations exhibit distinct features at short distances compared to the well-known far field or blackbody radiation. It is shown that the topography of the structure and local variations of its refractive index spatially modulate the vacuum field at the sub-wavelength level. This modulation can be measured with nano-optical probes using for example the fluorescence light of single emitters. Electrically conducting structures lead to thermal near field fluctuations that are enhanced by orders of magnitude compared to blackbody radiation. This determines fundamental limitations for the integration of coherent atom optical elements at the micron scale and below. We review methods to compute field fluctuation spectra in global or local thermodynamic equilibrium. The relevant background for fluorescence dynamics and coherent atom optics is summarized.