A JWST survey of the supernova remnant Cassiopeia A (Cas A) reveals detailed insights into the structure and composition of the remnant. Using NIRCam and MIRI imaging mosaics, the study maps emission from the main shell, interior, and surrounding circumstellar/interstellar material (CSM/ISM). Four exploratory positions of MIRI/MRS IFU spectroscopy sample ejecta, CSM, and associated dust from shocked and unshocked regions. Key findings include a web-like network of unshocked ejecta filaments, a thick sheet of dust-dominated emission from shocked CSM, and dozens of light echoes reflecting previously unseen fine-scale structure in the ISM. NIRCam observations place new upper limits on infrared emission from the neutron star in Cas A's center and tightly constrain scenarios involving a possible fallback disk. These results help address unresolved questions about massive star explosions, with implications for stellar population formation, galaxy metal and dust enrichment, and the origin of compact remnant objects. The study highlights the importance of high-resolution infrared observations in understanding the dynamics and chemistry of SNRs, and provides new insights into the formation and evolution of dust and molecules in these environments. The survey also reveals the complex structure of unshocked ejecta, including a web-like network of filaments and rings, and provides evidence for the presence of unshocked Fe in Cas A. The results are compared with radio and X-ray observations, and the study emphasizes the role of multi-wavelength observations in understanding the physical processes governing SNRs.A JWST survey of the supernova remnant Cassiopeia A (Cas A) reveals detailed insights into the structure and composition of the remnant. Using NIRCam and MIRI imaging mosaics, the study maps emission from the main shell, interior, and surrounding circumstellar/interstellar material (CSM/ISM). Four exploratory positions of MIRI/MRS IFU spectroscopy sample ejecta, CSM, and associated dust from shocked and unshocked regions. Key findings include a web-like network of unshocked ejecta filaments, a thick sheet of dust-dominated emission from shocked CSM, and dozens of light echoes reflecting previously unseen fine-scale structure in the ISM. NIRCam observations place new upper limits on infrared emission from the neutron star in Cas A's center and tightly constrain scenarios involving a possible fallback disk. These results help address unresolved questions about massive star explosions, with implications for stellar population formation, galaxy metal and dust enrichment, and the origin of compact remnant objects. The study highlights the importance of high-resolution infrared observations in understanding the dynamics and chemistry of SNRs, and provides new insights into the formation and evolution of dust and molecules in these environments. The survey also reveals the complex structure of unshocked ejecta, including a web-like network of filaments and rings, and provides evidence for the presence of unshocked Fe in Cas A. The results are compared with radio and X-ray observations, and the study emphasizes the role of multi-wavelength observations in understanding the physical processes governing SNRs.