Molecular biology has become unavoidable in almost all the different fields of biological science. After 1953, when Watson and Crick created the model for the DNA double helix, scientists started to annotate the genome to understand it more fully, for example, how the information encoded in our genes translated to phenotypic appearances. They aimed to find answers to questions such as: how were the different genes regulated or interacted with each other? How were the different genes transcribed onto messenger molecules to enable translation of the genomic code into native protein? What were the different roles for the proteins, what type of signal transduction system were they playing a role in? This interest was further fuelled after 2000 when the human genome was sequenced and became available to everyone. This chapter will guide you through the brief history of molecular biology, provide a general overview of the basic methods to study the different cellular mechanisms and highlight some of the applications which are currently in use during drug discovery research.