Recently, problems concerning order and disorder, coherence and incoherence, structure and chaos etc. have been lively discussed not only among physicists. As physicists, we should frequently be asked: what is the coherence which is used today in almost all branches of the sciences? how is this coherence defined exactly? what is the connection between structure and coherence etc. In this paper we try to show that 1) the concept of coherence is really rooted in the uncertainty principle of Heisenberg, the coherence space-time is identical to the uncertainty space-time for states of minimum fluctuations; 2) within the uncertainty (coherence) space-time we find structures of matter waves by using the general time-dependent Schrödinger equation, where the boundary condition plays an important role; 3) from this point of view we have a solid physical basis for understanding the principle of the "order-from-order" mechanism in the sense of Schrödinger [15].