Omics Big Data underpins genetic information and its expression for precision medicine, thereby accelerating the discovery of disease mechanisms, drug targets, and drug development. It has a wide range of applications, including clinical genomics and pharmacogenomics. This chapter offers a concise overview of various types of omics, current trends, and characteristics of the resulting omics big data. It also explores the applications of these data in the context of rare diseases, tumors, chronic diseases, and infectious diseases, along with the challenges of data sharing. The discussion primarily focuses on analyzing the ethical issues and challenges in clinical genomics and proposing ethical guidelines for clinical genomic testing and interpretation. These guidelines were published as an expert consensus.