Eclipsing binary (EB) is an interesting class of binary systems as EBs are key sources to determine stellar parameters with high precision.The photometric and radial velocity observations at different epochs is used to determine these parameters. Photometric observations alone can also determine parameters up to a good accuracy given the system is totally eclipsing binary. Long term period study can give additional information about presence of third body, probable mass transfer rates, magnetic activity cycle etc. Due to the presence of third body the O-C time of minima (TOM) observed at different cycles show cyclic behavior. In case of mass-transfer only, the O-C of TOMs is a curve and it is a straight line for systems having constant period. The long term surveys like SWASP, Kepler, TESS etc. provide high quality data for EB analysis.  In this talk, I am going to discuss the contact binary (CB) class of eclipsing binaries and present some of the results of our previously studied CBs.