In this chapter, we study von Neumann algebras in detail. We begin by showing that \({\mathcal {B}}(H)\) , and hence every von Neumann algebra, is a dual space. Then we study the tight relationship between normal and weak- \(*\) continuous homomorphisms. We show that every C*-algebra sits inside a universal von Neumann algebra. Then we characterize abstract von Neumann algebras as C*-algebras which are dual spaces. The last half of the chapter is devoted to the classification of von Neumann algebras into types, and exhibiting examples.