Disks and rings are present in different astronomical objects and at different scale sizes, from galaxies to stars and planets. Circumstellar disks orbit stars at different evolutionary stages and they are commonly detected as an infrared (IR) excess in their spectral energy distributions (SED). In the case of main sequence (MS) stars, an IR excess was first discovered in Vega (Aumann et al., 1984) with the Infrared Astronomical Satellite (IRAS). This finding, together with the discovery of the first exoplanet around the MS star 51 Pegasi by Mayor & Queloz (1995), opened a new era in the field of stellar astrophysics. After the discovery of the "Vega-like" phenomenon, a few other stars (Fomalhault, ε Eridani, β Pictoris) were also found to have an IR excess with fluxes at 25 µm and 100 µm significantly higher than those expected solely from the photosphere. The SED of this kind of excesses in the IR is consistent with models where dust particles in disks emit the extra energy, because they absorb the optical and ultraviolet light from the central star and re-radiate this energy thermally in the IR (Zuckerman, 2001). In Figure 1.1 we show the SEDs of the four stars showing the Vega-like phenomenon (sometimes known as the fabulous four).