Blue cheese is a generic term for a family of cheeses that have blue-green veins running throughout them. This distinctive marbling is more noticeable in some varieties than others, and sometimes the veins are visible on the outside of the wheel too. Like other types of cheese, blue cheese comes in many shapes and sizes. The taste of blue cheese is typically much stronger than other types of cheese. The blue-green veins are cultures from the mould Penicillium, which is safe to eat and gives the cheese its strong flavour and unique appearance.