Book excerpt: Even though molecular biology has long been a basic tool in biomedical research, scientists still face the question of why certain molecular biology methods are used for certain experiments. To unlock the mystery, one must first understand the principles behind the methods. Unfortunately, very few molecular biology books have successfully provided satisfactory explanations. This book intends to fill this void by offering topics ranging from basic knowledge to the current state of the art in applied molecular biology. The principles and applications related to each technique included in the text are all described in full detail.