The human genome has been sequenced, and investigation of its products has become possible in a sequence-based framework. More than 200,000 protein species are expressed in the body from approximately 30000 human genes. The term proteome, coined as a linguistic equivalent to the concept of genome, is used to describe the complete set of proteins that is expressed, and modified following expression, by the entire genome in a cell at any one time. Protein types and amounts expressed in a body vary greatly depending upon whether it is healthy or ill. Therefore, proteomics is attracting an increasing interest in its application to better understanding of disease processes, to development of new biomarkers for diagnosis and early detection of disease, and to accelerate drug development. There are numerous opportunities for medicine, although it is quite challenging to meet the needs for high sensitivity and high throughput required for disease-related investigations.