In this study, we have demonstrated that effective mixing can be achieved in simple and regular crossing channels. The dynamical processes combining split-and-recombine and chaotic mixing elements of stretching and folding were discussed. In channels with simple turns (up/down/right/left), flow could be stretched; on the other hand, tangential crossings could yield folding. Theoretically, repeating stretching and folding then result in the increase of interfacial area and decrease of striation thickness which facilitate the eventual mixing by diffusion. Practically, the structural sequence of turning and/or crossing affects the performance of the mixing. Three types of micromixers were studied, and the simulated performance was favorably compared with the published data. Experiments were carried out to qualitatively demonstrate the typical performance in the mixers. (C) 2010 American Institute of Chemical Engineers AIChE J, 57: 571-580, 2011