We present results on the study of 24 bulges of Sa galaxies observed with the integral-field unit SAURON at the William Herschel Telescope. Here we review some of the main features observed in our maps in terms of their kinematics and stellar populations, and unveil a rather complex picture in which the centers of spiral galaxies are made of several components: one (or more) thin, disclike component, often containing recent star formation, and another, elliptical-like component, consisting of old stars and rotating more slowly, dominating the light above the plane.