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This paper reports the results of a laboratory experiment on network formation among heterogeneous agents. The experimental design extends the basic Bala-Goyal (2000) model of network formation with decay and two-way flow of benefits by allowing for agents with lower linking costs or higher benefits to others. We consider treatments where agents' types are common knowledge and treatments where agents� types are private information. In all treatments, the (efficient) equilibrium network has a "star" structure. We find that with homogeneous agents, equilibrium predictions fail completely. In contrast, with heterogeneous agents stars frequently occur, often with the high-value or low-cost agent in the center. Stars are not borne but rather develop: in treatments with a high-value agent, the network's centrality, stability, and efficiency all increase over time. Our results suggest that agents' heterogeneity is a major determinant for the predominance of star-like structures in real-life social networks.