Abstract
In this article, we present an overview with the emphasis to highlight the basics of the origin of magnetism, size and shape effects on magnetic properties of materials and in particular the origin of nano magnetism which is also known as superparamagnetism when the size of the material particles lies between 1 and 30 nm. Besides this, a brief review of, various applications of the superparamagnetism in the areas like biosensors, data storage, drug delivery, and hyperthermia are discussed.