NOVELTY - Manufacturing at least portion of a processing apparatus, comprises: providing many metal layers; forming many metal layers (710, 720) into specific shapes; stacking and aligning the many formed metal layers; and connecting the formed metal layers together to form the portion of the processing apparatus, where the processing apparatus includes at least one fluid channel designed to process fluid flowing through it.    USE - The method is useful for manufacturing at least portion of processing apparatus, where the processing apparatus is used in chemical applications, biological applications, energy applications, pharmaceutical industry, and in applications that involves production of energy (fuel cells, solar cells, automotive fuel production from natural gas (Fischer-Tropsch process), methane processing, methanol production (methanol from carbon dioxide and hydrogen), production of alcohols from natural gas (methanol, ethanol), coal gasification processes, hydrogenation processes), propulsion systems (rocket engines), environmental waste processing (pollution and/or waste control systems, landfill gas processing, reduction of bio-waste, water purification systems, emissions control), biomedical applications (enzyme production), heat exchange application (furnaces), micro-electromechanical systems technology, avionics industry in fields of inertial measurement, RF technology, communications and micro-satellite components, biological, biotechnology and chemical industry in fields of microfluidics, microbiology, DNA assays and chemical testing, telecommunications industry in the fields of optical switches, displays, adaptive optics, and heat exchange industry, and/or extrusion industry (die plates, die insert, auger blades, wiper blades).    ADVANTAGE - The method provides processing apparatus which: creates intricate passageways in the micro reactor; has enhanced heat transfer capabilities; has ease of scale via adding additional micro-reactors on-line instead of past scale-up process; has ability to withstand high temperatures and/or pressures and immobilize catalysts to minimize diffusional mass transfer resistances and/or pressure drop; has ease of manufacture, and duplication; has ability to stack various modules or portions of micro-reactor together; minimizes capital investment and minimizes contamination of recovered catalyst; and has both low volume to surface area ratio and high degree of flow turbulence, thus controlling control chemical processes precisely.    DETAILED DESCRIPTION - INDEPENDENT CLAIMS are also included for:    (1) the processing apparatus, comprising the metal layers, where at least two of the metal layers includes a hole and/or slot, that is designed to allow fluid flow through it when the metal layers are connected together, at least two of the metal layers connected together by at least one laminate; and    (2) the processing apparatus designed enable a reaction or combustion of at least one fluid flowing through the processing apparatus, comprising an external system and metal layers that at least partially forms a fluid channel system, where at least two of the metal layers are stacked and aligned together and connected by at least one metal laminate, at least two of the metal layers includes an opening which is spaced from an outer edge of the at least two metal layers, the openings of adjacently positioned metal layers forming at least one fluid channel through the metal layers that is designed to enable fluid to flow through the at least one fluid channel when the metal layers are connected together, the external system is heating system, cooling system, magnetic field generator, an ultrasonic wave generator, sound wave generator, vibration generator or electromagnetic field generator, the external system designed to act on the fluid channel system to change a reaction rate of at least one component flowing through the fluid channel system, at least partially function as a catalyst or facilitator in a reaction of at least one component flowing through the fluid channel system, modify a structure of at least one component flowing through the fluid channel system, facilitate in or change a flow rate of at least one component flowing through the fluid channel system, change a density of at least one component flowing through the processing apparatus, a change of fluidity of at least one component flowing through the processing apparatus and/or a change of consistency of at least one component flowing through the processing apparatus.    DESCRIPTION OF DRAWING(S) - The figure shows a cross-sectional view of processing apparatus in the form of a furnace element.    Pipe (550)    Furnace element (700)    Metal layers (710, 720)    Passageway (730)    Gas port (740)