Microfluidics could enable us to analyze cells and tissues with much higher resolution in space and time.Small dimensions of the microfabricated structure comparable to the size of cells could lead to confinement of small number of cells into the microfabricated spaces,leading to the analysis at the single-cell level.The confinement of molecules into a small space is also beneficial to highly sensitive detection of small number of molecules.The specific characteristics of the low Reynolds number flow could be useful to form laminar flow streams over a micrometer-sized space to culture cells.Local culture conditions can be controlled flexibly and stably by the laminar flow streams containing different types of soluble factors affecting on,for example,the cell fate,such as differentiation vs.undifferentiated(pluripotent)state.