Whereas IRAS provided the first systematic survey of far-infrared (FIR) emission from normal galaxies, it has been the photometric, imaging and spectroscopic capabilities of the ISOPHOT instrument (Lemke et al. [51]) on board the Infrared Space Observatory (ISO; Kessler et al. [47]) which have unravelled the basic physical processes giving rise to this FIR emission. Thanks to the broad spectral grasp of ISOPHOT, the bulk of the emission from dust could be measured, providing the first quantitative assessment of the fraction of stellar light re-radiated by dust. The battery of filters has led to a definitive characterisation of the spectral energy distribution (SED) in the FIR, revealing the contribution of the different stellar populations in powering the FIR emission. The imaging capabilities have unveiled the complex morphology of galaxies in the FIR, and their changing appearance with FIR wavelength. They also allowed the exploration of hitherto undetected faint diffuse regions of galaxies.
In this review we will concentrate on the FIR properties of normal nearby galaxies. By normal we essentially mean that their SEDs are not powered by accretion. We will begin with spiral galaxies and then we will move to the other class of gas-rich galaxies, the dwarfs.