Photometric variability of the Pre-Main sequence stars

The photometric and spectral studies of the pre-main sequence stars are very important for understanding of the early stages of stellar evolution. Depending of the initial mass the young stars pass through different periods of stellar activity. The most prominent manifestations of this activity are changes in the star brightness with different periods and amplitudes. A short review on photometric variability of young stellar objects is presented in the paper. The physical mechanisms raising the photometric variability were summarized according to the main types of pre-main sequence stars. The importance of photometric and spectral observations of young variable stars with small telescopes is discussed.