The contents of this book deal with isomorphic embeddings and factorizations of certain operators. Chapter I discusses the significance and important results of embeddings and factorizations of Banach spaces. Chapter II introduces notations and preliminary materials that are needed for presenting the main theorems. Chapter III gives an intrinsic characterization of subspaces and quotients of Banach spaces with unconditional bases which solves a long standing problem in this field. Results of operators on Lp which factor through lp are contained in Chapter IV and further extensions of operators which factor through Banach spaces with asymptotic structures are discussed in Chapter V. The last Chapter summarizes the main results of the book and provides some related open problems.