Silk glands of silkworm can be divided into anterior (ASG), middle (MSG), and posterior (PSG) parts, each with a unique function in cocoon formation. The silk protein is synthesized by cells of the silk gland and stored in the lumen of the silk glands. The silkworm silks are broadly classified as mulberry and wild or non-mulberry according to the feeding habits of silkworms. There are different methods used for extraction of sericin from cocoons of silkworms that have an effect on the yield of sericin. Silk sericin provides an important set of material options in the fields of tissue engineering and drug delivery. The effectiveness of interaction of any new material with the host immune system and assessment of its biocompatibility is necessary before long-term in vivo use. Due to its various biological properties, sericin is also becoming a potential natural silk protein material in the pharmacological, biomedical and biotechnological fields. © 2016 by John Wiley & Sons, Inc. All rights reserved.