The global properties of all variety of AGN
  Active Galactic Nuclei (AGN) have been a challenging field of research for the past six decades. Nevertheless, many questions still remain unanswered today, regardless of the tremendous theoretical and technological advances. In this brief review I propose to take a step back from the usual discussion of AGN properties and draw attention to some topics that I believe are important to keep in mind as we strive forward in our pursuit of knowledge about these sources. 
M.J.M. Marcha (Observatorio Astronomico de Lisboa, Portugal)