The detailed design stage includes the complete specification of the geometry, materials and tolerances of all the unique parts in the product and the identification of all standard parts to be purchased from suppliers.  The output of this stage is the control documentation for the product, the drawings and CAD files describing the geometry of each part and the process plans for the fabrication and assembly of the product.

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The product's architecture begins to emerge during concept development.  This happens informally in the sketches, function diagrams, and proof of concept prototypes of the concept development phase.  The architectural decisions now must be formalized after the final product concept has been selected, but before detailed design begins.  This occurs during the system level stage of development.