Forming limit diagram (FLD) is an important tool in analysis of sheet metal forming process, as it defines failure criteria. But the forming of microthin sheets (thickness <100 µm) is prone to more defects and requires more precision. The process is termed as microforming and is gaining more attention of researchers due to its miniaturization in many fields. Many variations occur in the properties of material at microthickness level. So new failure criteria must be defined for microthin sheets. In this chapter, experimental investigations for 40 and 90 µm thin brass foil along with different rolling directions (0, 45, and 90 degrees) to plot FLD are presented. Hemispherical punch test is performed according to ASTM-2218-14 standard test using uniaxial strain, plane strain, and biaxial strain specimen. The results are compared for different thicknesses and rolling directions.