The book focuses on interesting topics in plant biotechnology and its applications. The first section covers a number of specific medicinal plants and their secondary metabolites using genetic and metabolic engineering. The pharmaceutical uses of these plant bioactive compounds and their applications in treating a variety of diseases including cancer, as well as recent works on in silico and bioinformatic analysis are described. The second section deals with innovative plant molecular pharming approaches and reviews the potential for using various plant host systems to design and produce effective new drugs to treat different illnesses and diseases such as HIV, infectious diseases, and other human and livestock diseases.