Cell-to-cell communication is considered to underlie the coordinated behavior and the multicellularity of cell group class, which cannot be explained only by the knowledge of lower class of life system from molecule to individual cell, because they are determined by at least two different ways: diffusible chemical signals and their direct physical contacts. We show in this paper a new method of individual-cell-based cell observation that can estimate the role of cell-to-cell communication, diffusible chemical signals, and physical contacts as separated properties, by applying an on-chip individual-cell-based cultivation system. The exchange of stationary phase medium on isolated individual Escherichia coli from exponential phase medium and the control of physical contacts indicated that the cell-to-cell direct contact did not affect the growth rate; only the communication through diffusible signals affects the growth rates as Hill's equation manner. (c) 2006 Elsevier Inc. All rights reserved.