The Bulge of M31

Bulges are not just elliptical subgalaxies situated in the centers of large spirals, though it might seem so from their ages and chemistry. In fact, bulge kinematics have been known to be different since the first long slit spectra were obtained. M31 presents the best opportunity to investigate all the issues of the stellar populations of bulges. This review collects the array of probing data that has been accumulated during the last decade. But the intriguing question 'how did it form like this?' remains.