3D IC is the viable revolutionary technology that will enable system-level integration, miniaturization, optimal power management, increased data bandwidth, and eventually reduced system cost. Like any breakthrough technologies, it faces many challenges. Design methodology, integration technology, manufacturing process and new industrial ecosystem are the areas of focus. This paper will discuss these challenges and Altera's 3D integration development effort. 2.5D is an intermediate path to true 3D IC using silicon interposer and TSV (Through-Si-Via) stacking. The 2.5D stacking configuration offers different form factor, interconnect path, and thermal management options than monolithic packages, which could help to reduce system level power and thermal management pressure. It offers silicon level interconnect density, low inductive path and wide IO application. However, it's power delivery system (PDN) could be the bottleneck for the system to perform at the intended bandwidth and speed. Thus, the whole sy...