Abstract: By providing two, interconnected fluid storing containers, each of which comprise piston members sealingly engaged therewith and manually movable along the inside surface thereof, a unique, linear gradient former is achieved which is capable of controllably providing precisely mixed linear gradients. In addition, the linear gradient former of the present invention is usable to quickly, easily, and precisely fill the fluid holding chambers, by manually moving the pistons in an opposite direction. One of the fluid storing containers incorporates outlet means for delivering the linear gradient to the desired chamber for use and, in the preferred embodiment, also incorporates fluid mixing means to assure uniform distribution of the fluids in the container prior to being dispensed.