Current understanding of cellular system in the modern biochemistry/molecular biology is mainly based on the deterministic analysis. Although this helped mechanical understanding of cellular processes such as cell growth or differentiation at molecular levels, actual these cellular systems are not rigid systems like a machine but produce unexpected stochastic behaviors; fluctuations or variations. This is uncovered along with the development of bio-imaging techniques. Now in these days, we encounter with the fact that cells actually accept and rather utilize these fluctuation/variations to survive and adapt under variable circumstances. In my lab, we are trying to clarify dynamic biological systems such as genome stress response, nutrition restriction and/or cell differentiation, based on “fluctuation” and “noise”.