The trend in life science areas is the explosion of data, which is occurring in every hierarchy of life, e.g. molecular, cellular, tissue and organ levels, due to the development of experimental technologies. For instance, thousands or tens of thousands of individual genomes are going to be sequenced all over the world. Gene expression data and protein structure and function data have also been accumulated. In addition, cellular and organ-level data such as neurological activities in brain and images of organ development are also recorded. The development of biobanks, which collects both clinical and biological data of humans, paves the way to for personalized medicine, in which the best therapy is selected for each individual. Such "big data" provides us with an opportunity to understand life more extensively, but to extract as much knowledge as possible information science plays an crucial role in realizing tailor-made analysis of these diverse ranges of data. Thus, the role of bioinformaticists in biology is now enlarging. We are developing methods to analyze biological data based on information theory to understand the systems of life and to help people live healthier.