Abstract
People have long asked, “What is the world made of ?” and “What holds it together ?”. People have come to realize that the matter of the world is made from a few fundamental building blocks of nature. By fundamental building blocks we mean objects that are simple and structureless not made of anything smaller. The subject of this lecture is to present a sketch of the understanding we have today of what we consider to be fundamental building blocks or fundamental particles and the interactions between them. By adopting a semi-historical path, we shall meander through a century or so of discoveries which have led to the establishing of the currently accepted picture and outline some of the outstanding unsolved problems of this picture.