A process for forming a multi-well plate with wells, said process comprising: (a) forming a plate blank from a plastic resin by single-shot injection molding, said plate blank having an initial thickness and comprised of a deck portion and an array of rudimentary wells, each rudimentary well comprising an upper lateral wall section, a lower lateral wall section and a floor, each upper lateral wall section comprising a straight cylindrical section or neck, and each lower lateral wall section comprising a frustoconical shape between the neck and the floor; (b) placing the plate blank so formed in a vacuum forming mold, the vacuum forming mold comprising an array of depressions aligned with the rudimentary wells, each depression configured to accommodate one rudimentary well, wherein each depression is complementary in shape to the upper lateral wall section of a rudimentary well and comprises a lower portion that extends below the lower lateral wall section of a rudimentary well accommodated in the depression, and a vent hole in the lower portion; and (c) with the plate blank so placed, applying a pressure differential across the lower lateral wall sections of the rudimentary wells, thereby drawing resin of the lower lateral wall sections into the lower portions of the depressions, to selectively stretch and reduce the thickness of said lower lateral wall sections and to fill the entire depression while leaving said deck portion, upper lateral wall sections and the floor unstretched and substantially thicker than said lower lateral wall sections, wherein the vacuum forming mold and the plate blank are heated during the applying of the pressure differential. (a) forming a plate blank from a plastic resin by single-shot injection molding, said plate blank having an initial thickness and comprised of a deck portion and an array of rudimentary wells, each rudimentary well comprising an upper lateral wall section, a lower lateral wall section and a floor, each upper lateral wall section comprising a straight cylindrical section or neck, and each lower lateral wall section comprising a frustoconical shape between the neck and the floor; (b) placing the plate blank so formed in a vacuum forming mold, the vacuum forming mold comprising an array of depressions aligned with the rudimentary wells, each depression configured to accommodate one rudimentary well, wherein each depression is complementary in shape to the upper lateral wall section of a rudimentary well and comprises a lower portion that extends below the lower lateral wall section of a rudimentary well accommodated in the depression, and a vent hole in the lower portion; and (c) with the plate blank so placed, applying a pressure differential across the lower lateral wall sections of the rudimentary wells, thereby drawing resin of the lower lateral wall sections into the lower portions of the depressions, to selectively stretch and reduce the thickness of said lower lateral wall sections and to fill the entire depression while leaving said deck portion, upper lateral wall sections and the floor unstretched and substantially thicker than said lower lateral wall sections, wherein the vacuum forming mold and the plate blank are heated during the applying of the pressure differential.