The objective of this research was to create a 3D in vitro model to mimic the native breast tumor microenvironment. Polydimethylsiloxane (PDMS) stamps and micromolding techniques were utilized to develop collagen based 3D tumor model. Geometrical design was optimized for the PDMS stamp to compartmentalize the tumor and stromal region of the 3D model. Addition of tumor and stromal cells into the platform further demonstrated the successful fabrication of the 3D model which will be used to investigate the role of stromal components on tumor growth and progression. Atomic force microscopy will also be utilized to access stromal remodeling during active invasion.