Please help to summarize it into 50 words, thanks. Rennet is an enzyme responsible for curdling milk to separate the curds and whey and the beginning of the process to make cheese. Milk is full of protein molecules; most of these (>80%) are formed into the casein micelle. One part of this is micelle (kappa casein: located on the extremity of the micelle) is negatively charged. This means it repels the other casein micelles, causing milk to stay in its liquid form. Rennet contains an enzyme(chymosin) which cuts this negatively charged kappa casein protein so that negative end of the chain dissolves into the liquid. This is the primary phase of coagulation. In secondary phase, the proteins no longer repel each other and start to join together. This happens because the freshly cut kappa casein is sensitive to picking up minerals. Its cut end links with phosphate and then calcium minerals present in milk to form a bridge that joins the casein micelles together. As the proteins join together to form the curd/junket, the web also traps in the fats and minerals and this junket will go on to form the cheese (THE COURTYARD DAIRY).