This seminar is devoted to hydrodynamic combustion like instabilities in different media, namely in laser ablation, organic semiconductors and molecular magnets. Laser ablation will be compared with combustion wave and I will show our results in Darrieus-Landau instability in ablated flow. Doping front in organic semiconductors provides another very interesting example of combustion like unstable flow. Our theory, experiments and numerical results will be presented and discussed. Finally crystals of molecular magnets are considered from magnetic combustion point of view. As an example, it is shown that thermal-diffusion instability can take place in these crystals.