A major objective of 'omics' technologies is to understand genetic causality of complex traits of human diseases. High-throughput omics technologies and their application to medicine open up remarkable opportunities for realising optimised medical treatment for individuals. Because many major breakthrough and discoveries in this field have been driven by the development of new omics technologies, in this review, the authors aim to provide an in-depth description of their underlying principles as a foundation of developing another new omics technology, and to introduce their emerging applications for personalised medicine. The systems biology approach is then introduced as a future direction towards actionable personalised medicine.