Active galactic nuclei (AGN) are among the most interesting astrophysical objects in the Universe. IAU Symposium 304, dedicated to marking the centenary of B. E. Markarian's birth, addresses the most important questions in this area: understanding the possible evolutionary and/or physical connections between the different classes of AGN; the relation of AGN to their host galaxies; and understanding the true fraction of heavily obscured AGN in order to determine the true AGN luminosity function and its variation with redshift. This volume's topics include: historical spectral and colorimetric surveys, multiwavelength AGN surveys, AGN statistics, unification and other models of AGN, AGN feedback in galaxies and clusters, their host galaxies and environments, binary AGN and merging supermassive black holes, AGN variability, and future large projects. This fresh summary of AGN surveys is especially useful for researchers engaged in this exciting field and helping them plan for future surveys and observations.