This symposium is explicitly devoted to Planetary Nebulae which are associated to “dying” stars of moderate mass. All other bright nebulae in the Galaxy can be considered to be related to planetary nebulae in the sense that they are similar to planetary nebulae in many respects. However, in most cases, these “relatives”-nebulae correspond to astro-physical situations (as characterized by the evolutionary stage, chemical composition, physical parameters, etc.) which are completely different. A large variety of nebulae can be found in the sky. One goes from point-like objects like K3-50, which is a very compact HII region, or V1016 Cyg, possibly a proto-planetary nebula, through moderate size nebulae like the Crab Nebula (the famous supernova remnant, 5′ size) or the Orion Nebula (the famous HII region around the Trapezium stars, 3′ core), to large nebulae like the Trifid (HII region of 20′ size) or NGC 6888 (which is associated to a WN6 star, about 30′) and extremely large like the North America Nebula (NGC 7000, an emission-reflection nebula of about 2° size) and the Gum Nebula (probably a supernova remnant of approximately 36° diameter). We see that not only might they be different in size but also, and drastically, different in their physical nature. It is interesting to note, however, that as a rule nebulosities are found to accompany stars only in the early phases and in the very late phases of evolution. At this stage of the symposium we should have learned enough about nebulae related to old stars. Therefore, I have decided to talk about nebulae related to stars at the other end of evolution, that is classical HII regions. For convenience, I will use here the term “HII region” meaning implicitly an ionized nebula associated to, and ionized by, a young and massive star. By definition, these nebulae are interesting because they represent the first manifestation of new-born stars of high mass. In fact, in many cases one can detect an HII region (in the radio and/or in the infrared) well before being able to directly observe the exciting star.