Publisher Summary This chapter outlines the effects of buffer electroosmotic mobility, sample diffusion coefficient, sample electrophoretic mobility, the conductivity difference of the solutions, the applied field strength, and the channel size on the loading and dispensing processes. By understanding the complicated electrokinetic processes involved in the sample dispensing processes, one can find optimal applied voltages and the improved methods to control the size, shape, and concentration of the dispensed samples. The chapter focuses on the electrokinetic sample dispensing or injection processes in a crossing microchannel structure. The perpendicular intersection of the two microchannels is of particular importance for two reasons. Firstly, it represents the most fundamental unit of more complicated, grid-like, microchannel networks; secondly, it can be used, in conjunction with electroosmotic flow, to realize discrete sample injections. It discusses that the studies of the on-chip sample injection started with capillary electrophoresis separation. The feasibility of using electroosmotic pumping to transport liquids in a manifold of channels and the possibility of conducting the electrophoretic separation on a planar substrate has been examined and demonstrated. The experiment focused on the design and testing of microfluidic devices and did not investigate how to control the microfluidic processes in such devices. Toward this end, most on-chip dispensing efforts to date have been concerned with tightly focused samples and high electric field strengths.