In the last years our knowledge of the chemical complexity in the nuclei of galaxies has dramatically changed. The availability of wideband more sensitive receivers in single dish telescopes has provided a complete chemical description of the nucleus of the Milky Way and of the starburst galaxies like NGC253 and M82, as well as the detection of complex organic molecules in the Ultraluminous Galaxy (ULIR) Arp220. We measure large abundance of methanol in starburst galaxies and ULIRs suggesting that complex organic molecules are also efficiently produced in the central region of galaxies with strong star formation activity. From the systematic observational studies of molecular abundance in regions dominated by different heating processes like shocks, UV radiation, X-rays and cosmic rays in the center of the Milky Way, we are opening the possibility of using chemistry as a diagnostic tool for studies of galactic evolution, star formation, starbursts and feedback in the highly obscured regions of galactic centers. I will present recent advances of molecular observations in external galaxies. The templates found in the nucleus of the Milky Way will be used to establish the main mechanisms driving the heating and the chemistry of the molecular clouds in galaxies with different type of activity. The role of grain chemistry in the chemical complexity observed in the center of galaxies will be also briefly discussed.