The luminosity of the bulge was an important parameter in the early classification of galaxies. Later a large dispersion was found between the bulge-to-total (B/T) mass ratio and the morphological type, but B/T is still expected to have a fundamental role in the evolutionary picture of galaxies. For example the B/T, together with the shape parameter of the bulge, is crucial for evaluating when bulges were formed in galaxies: in the primordial collapse, in galaxy mergers in the hierarchical clustering, or relatively recently by more slow secular evolutionary processes in galaxies? B/T-ratio is also a key parameter for evaluating the importance of gas stripping in galaxies, a process by which spirals might be converted into S0s. The mass of the bulge has also repeatedly been found to be correlated with the mass of the supermassive central black hole. In order to evaluate galaxy evolution in the Hubble sequence, the B/T-ratios need to be estimated using a similar structural decomposition method for all morphological types. It is also of crucial importance to take into account, not only the bulges and disks, but also bars and ovals, since many bars and ovals appear frequently particularly in early-type disk galaxies. The statistically well defined data-bases - OSUBGS (Ohio State University Bright Galaxy Survey) for spirals and NIRS0S (Near-InfraRed S0 Survey) for S0s, as well as the recent development of multicomponent decomposition methods, have made possible, for the first time, a uniform estimation of B/T-ratios in the Hubble sequence .