The article reviews the development, challenges, and opportunities of van der Waals (vdW) integration, a bond-free material integration strategy that uses weak vdW interactions to physically assemble pre-fabricated building blocks. This approach offers a flexible and low-energy method for integrating diverse materials, particularly two-dimensional (2D) atomic crystals, without the constraints of strict lattice matching or processing compatibility. The review highlights the potential of vdW integration in creating artificial heterostructures and superlattices with atomically clean and electronically sharp interfaces, enabling the fabrication of high-performance devices such as transistors, photodiodes, and optoelectronic devices. The article also discusses the historical background, current state-of-the-art vdW heterostructures, and the unique opportunities and challenges arising from vdW integration, including tunable metal/semiconductor junctions, pinning-free interfaces for coherent transport, heterogeneous-layer assembly by design, and vdW sliding interfaces. Finally, it addresses the outlook for scalable system-level integration and the technical challenges that need to be overcome to realize the full potential of vdW integration in practical technologies.The article reviews the development, challenges, and opportunities of van der Waals (vdW) integration, a bond-free material integration strategy that uses weak vdW interactions to physically assemble pre-fabricated building blocks. This approach offers a flexible and low-energy method for integrating diverse materials, particularly two-dimensional (2D) atomic crystals, without the constraints of strict lattice matching or processing compatibility. The review highlights the potential of vdW integration in creating artificial heterostructures and superlattices with atomically clean and electronically sharp interfaces, enabling the fabrication of high-performance devices such as transistors, photodiodes, and optoelectronic devices. The article also discusses the historical background, current state-of-the-art vdW heterostructures, and the unique opportunities and challenges arising from vdW integration, including tunable metal/semiconductor junctions, pinning-free interfaces for coherent transport, heterogeneous-layer assembly by design, and vdW sliding interfaces. Finally, it addresses the outlook for scalable system-level integration and the technical challenges that need to be overcome to realize the full potential of vdW integration in practical technologies.