In the previous chapters, we discussed only dust-filled cosmological models, showing the observational evidence for dark energy. It is interesting to note how three different class of observations aimed to estimate the Hubble constant, the age of the universe and the luminosity distance from SNe Ia excluded the simple Einstein-de Sitter model, with a clear preference for a flat concordance model with Ω0 ≃ 0.3 and ΩΛ ≃ 0.7.