  Some of the basic concepts of topology are explored through known physics
problems. This helps us in two ways, one, in motivating the definitions and the
concepts, and two, in showing that topological analysis leads to a clearer
understanding of the problem. The problems discussed are taken from classical
mechanics, quantum mechanics, statistical mechanics, solid state physics, and
biology (DNA), to emphasize some unity in diverse areas of physics. It is the
real Euclidean space, $R^d$, with which we are most familiar. Intuitions can
therefore be sharpened by appealing to the relevant features of this known
space, and by using these as simplest examples to illustrate the abstract
topological concepts. This is what is done in this chapter.
