Photosensitive polyimides (PSPIs) are transforming RF microsystem design by enabling high-frequency performance, compact layouts, and simplified manufacturing. With their low dielectric constant, excellent thermal stability, and UV-patternable nature, PSPIs are ideal for RF filters, interconnects, and advanced packaging. As systems push into 6G and terahertz domains, PSPIs are proving to be an invisible yet indispensable design advantage.