Phycocyanin is a phycobiliprotein pigment primarily found in cyanobacteria such as Spirulina platensis and some red algae, where it functions as a light-harvesting antenna in photosynthesis, absorbing light in the 550-650 nm range and transferring energy to chlorophyll. It consists of an alpha and beta subunit forming a heterodimer, with a phycocyanobilin chromophore covalently attached, giving it a vibrant blue color. Chemically, it is a water-soluble globular protein with antioxidant, anti-inflammatory, and potential neuroprotective properties, often studied for its role in mitigating oxidative stress and as a natural food colorant (E-number E133 in some regions). Phycocyanin is extracted for use in the food, cosmetic, and pharmaceutical industries due to its stability in aqueous environments and health benefits, including possible anticancer and immunomodulatory effects as indicated by in vitro and animal studies. It is heat-sensitive, denaturing above 50-60°C, and pH-dependent for optimal stability. Research from peer-reviewed sources, such as journals from the American Chemical Society, highlights its non-allergenic nature and bioavailability when consumed orally. With a minimum molecular weight of about 17,000-30,000 Da, it is valued for its natural origin and safety profile, making it a popular alternative to synthetic dyes. Its extraction involves aqueous methods, and it has been extensively reviewed in biochemical literature for applications in nutrition and biotechnology.