systems having passage cross sections in the range of tens of square microns to a few square millimeters or having flow rates in the range of from a few nl sec to a hundreds of u03bcl sec the number of fluid flows controlled by fluidics circuits of the invention can vary widely in one aspect fluidics circuits of the invention control a plurality of flows in the range of from 2 to 12 different fluids or in another aspect in the range of from 2 to 6 different fluids the design and operation of one embodiment of the invention is partially illustrated in fig1 a four fluid inlets or reagent inputs 100 102 104 106 are connected to fluidics node 108 and are in fluid communication with and on an opposing surface to outlet 110 valve 111 is shown open so that fluid passes through inlet 100 into fluidics node 108 a portion 124 of the fluid travels through a passage shown on the left a portion 126 travels through a passage shown on the right and a portion exits the fluidics node through outlet 110 preferably the three fluid flows are laminar and the flow along the surface containing the fluid inlets exits the fluidic node in a period of time that is much less than the time it would take material from the unselected inlets diffuse effluent 128 to diffuse to the opposing surface of the fluidics node in this way intermixing of the different input reagents that exit through outlet 110 is avoided in one mode of operation reagent inputs are selected by opening the valve corresponding to such reagent and closing all the other valves.