The ICG (Indocyanine Green) series comprises clinically proven tricarbocyanine fluorophores optimized for near-infrared (NIR) imaging (λex/em ~780/820 nm). These hydrophilic dyes exhibit exceptional deep-tissue penetration (up to 1-2 cm) with minimal autofluorescence interference, making them indispensable for real-time surgical navigation, lymphatic mapping, and organ function assessment. Featuring versatile reactive derivatives (e.g., NHS ester, carboxylate, azide), they facilitate stable bioconjugation while maintaining ICG's established safety profile. Their intrinsic protein-binding capability enhances biodistribution, enabling applications in angiography, photothermal therapy, and image-guided oncology.