[en] It is pointed out that the outer parts of galaxies often exhibit distinct surface brightness enhancements. The development of rings and shells around galaxies has been ascribed to mechanisms in which the interaction of a galaxy with its neighbors plays a key role. According to some concepts, the big events, such as those leading to the formation of ring galaxies, are interspersed with an entire set of smaller ones. In particular, small galaxies in a group are inclined to fall into their bigger neighbors without affecting the latter very much. After the event, the big galaxy is provided with certain features, taking into account ellipticals with shells, and S0s with polar rings. A review is conducted of the properties of these types of galaxies, insofar as their outskirts have identifiable shells or rings. Attention is given to ring galaxies, outer rings around spirals and S0s, polar ring galaxies, and shells around elliptical galaxies. 157 references