This paper presents Pneumatic Auxetics, an inverse optimization method for designing and fabricating morphing three-dimensional shapes out of patterns laid out flat. In origami/kirigami research, optimization of patterns that can be transformed into the target surface by inverse design has been attempted. On the other hand, in the research area of pneumatically actuated geometries, the control of the transformation using skeletons and membranes has been attempted. In the study of the inverse design of the auxetic pattern based on kirigami, it cannot actuate deformation by removing air because the design does not consider the thickness. Therefore, we simulate the pneumatic transition with the thick shell structure that is generated by offsetting the input surface (Figure 1). The designed skeleton is optimized for FGF (Fused Granular Fabrication) 3D printing, and it is 3D printed using soft elastomeric materials. These allow for both a deformable hinge and a rigid pattern. Thus, a skeleton made of a single material can be deformed to approximate the shape of the target-input surface by placing it in a membrane and removing the air. In this paper, we introduce related works and research contexts, challenges, inverse design simulator and its fabrication by 3D printing, and potential future applications.