A sole structure for an article of footwear, the sole structure comprising: an outer member comprising a base portion and a plurality of ground engaging members (122, 200, 242, 244, 246, 248, 250, 252, 276, 312, 314, 316, 318) extending away from the base portion, wherein the outer member further comprises apertures comprising a hollow interior region that is bounded by the ground engaging members (122, 200, 242, 244, 246, 248, 250, 252, 276, 312, 314, 316, 318), the apertures forming three-pointed star-shaped openings in outer member, wherein the outer member comprises a regular pattern of triangular-shaped outer member areas (272, 296, 297, 298), each triangular-shaped outer member area (272, 296, 297, 298) being disposed between adjacent ground engaging members (122, 200, 242, 244, 246, 248, 250, 252, 276, 312, 314, 316, 318); wherein each of the ground engaging members (122, 200, 242, 244, 246, 248, 250, 252, 276, 312, 314, 316, 318) comprises six faces (290, 291, 292, 293, 294, 295) extending from a base portion; wherein each of the six faces (290, 291, 292, 293, 294, 295) is joined at an apex (204, 266, 268, 270) of the respective ground engaging member (122, 200, 242, 244, 246, 248, 250, 252, 276, 312, 314, 316, 318); and wherein the plurality of ground engaging members (122, 200, 242, 244, 246, 248, 250, 252, 276, 312, 314, 316, 318) is configured in a geometric pattern that provides an auxetic structure to at least some portions of the sole structure such that when the auxetic structure is placed under tension in a first direction, the auxetic structure can increase in size both in the first direction and in a second direction that is orthogonal to the first direction. an outer member comprising a base portion and a plurality of ground engaging members (122, 200, 242, 244, 246, 248, 250, 252, 276, 312, 314, 316, 318) extending away from the base portion, wherein the outer member further comprises apertures comprising a hollow interior region that is bounded by the ground engaging members (122, 200, 242, 244, 246, 248, 250, 252, 276, 312, 314, 316, 318), the apertures forming three-pointed star-shaped openings in outer member, wherein the outer member comprises a regular pattern of triangular-shaped outer member areas (272, 296, 297, 298), each triangular-shaped outer member area (272, 296, 297, 298) being disposed between adjacent ground engaging members (122, 200, 242, 244, 246, 248, 250, 252, 276, 312, 314, 316, 318); wherein each of the ground engaging members (122, 200, 242, 244, 246, 248, 250, 252, 276, 312, 314, 316, 318) comprises six faces (290, 291, 292, 293, 294, 295) extending from a base portion; wherein each of the six faces (290, 291, 292, 293, 294, 295) is joined at an apex (204, 266, 268, 270) of the respective ground engaging member (122, 200, 242, 244, 246, 248, 250, 252, 276, 312, 314, 316, 318); and wherein the plurality of ground engaging members (122, 200, 242, 244, 246, 248, 250, 252, 276, 312, 314, 316, 318) is configured in a geometric pattern that provides an auxetic structure to at least some portions of the sole structure such that when the auxetic structure is placed under tension in a first direction, the auxetic structure can increase in size both in the first direction and in a second direction that is orthogonal to the first direction.