In this thesis, the main features of cephalopod ink are presented. Cephalopod ink is the product of the secretions of two glands. The ink sac gland produces ink which contains melanin, responsible for the black color. The second gland, the funnel organ, produces mucus, but it is poorly studied. The most important role of ink is a defense against predators. Discharged ink can take several forms, namely diffuse clouds that contain relatively little mucus, denser clouds with more mucus named pseudomorphs, and slimy, thin, long secretions called ropes. Also, ink has great importance for human use, with an emphasis on medical and scientific research purposes. Recently, ink has increasingly being used to find new drugs, and research of antimicrobial, anti-cancer and anti-inflammatory properties of ink is becoming more common.