The properties of random lasers in pi -conjugated polymer films and solutions infiltrated into opal photonic crystals are viewed. We show that random lasing is a generic phenomenon that occurs in disordered gain media at an excitation intensity regime higher than that giving rise to amplified spontaneous emission. The emission radiation is coherent as demonstrated by photon statistics methods, and it spectrum contains many laser modes from which a typical cavity length can be obtained using Fourier transform spectroscopy. Since the random cavities are independent from each other, we show that laser emission in several colors is possible when mixing different dyes in the same random cavities, In addition, it is demonstrated that random lasing is formed in many disordered media with various scattering properties ranging from a regime of light prelocalization to that of weak scattering.