Iodine is a widely known halogen element with an excellent dual reputation in human nutrition and infection safety. It exists naturally in seawater and underground mineral brine deposits. Although it is needed by the body only as a trace nutrient, iodine is highly essential for making thyroid hormones that regulate metabolism, control energy generation, manage body temperature, maintain heartbeat rhythm, support brain development, and help bones grow stronger. Since iodine cannot be made within the body, external food or fortified salt sources serve daily iodine needs. Seafood such as fish, shellfish, crab, lobster, and edible seaweed provide naturally occurring iodine due to ocean-water absorption. Meanwhile, iodized salt remains the most globally trusted and easily available iodine source added to meals in measured portions. Outside nutrition, iodine stands out for powerful antiseptic behavior. It kills harmful bacteria, viruses, fungi, and surface microbes very effectively. This makes iodine useful for first-aid wound cleaning, skin sterilization before medical procedures, and general infection prevention when applied in controlled medical-grade portions. Iodine’s solid form looks like shiny dark purple crystals, and when heated, evaporates into purple vapor through sublimation. Iodine-based sheets and compounds are also used in medical imaging contrasts and diagnostic scanning systems. Though iodine is extremely helpful, balance remains important, as both deficiency and excess intake can affect thyroid performance. Its role remains meaningful in both lab science and real-world health and hygiene support.