We study nematic LCs and nematic colloids flowing through microchannels using polarizing transmission microscopy and fluorescence confocal polarizing microscopy. Depending on the channel dimensions, the anchoring conditions on the channel walls, and the flow rate, the formation of different textures and defect structures is observed: -walls, disclination lines (DL) pinned to the channel walls, DL with one pinned and one freely floating end, and DL and loops freely floating in a chaotic-like manner. Preliminary observations of nematic LCs containing colloidal particles indicate that textures and defects of the nematic matrix can be used to guide the transport of the particles through the microchannels.