Heat generation in high-performance three-dimensional integrated circuits (3D ICs) is a significant challenge due to limited heat removal paths and high power density. To address this challenge, this paper presents an embedded microfluidic heat sink (MFHS) for such high-performance 3D ICs. In the proposed 3D IC system, each tier contains an embedded MFHS, along with high-aspect-ratio (23:1) through-silicon vias (TSVs) routed through the MFHS. In each tier, solder-based electrical and fluidic inputs/outputs are co-fabricated with wafer-level batch fabrication. Moreover, microfluidic cooling experiments of staggered micropin-fins with embedded TSVs are presented for the first time.