Blue cheese is a type of cheese with blue or green veins running through it, created by adding special mold during the cheese-making process. The mold (usually Penicillium roqueforti) gives blue cheese its distinctive appearance and sharp, tangy flavor that some people love and others find too strong.

When you cut open a wheel of blue cheese, you'll see marbled streaks of blue-green mold spreading through the white or yellowish cheese, almost like tiny rivers on a map. The mold isn't dangerous: it's carefully cultivated and gives the cheese its characteristic strong taste and smell.

Famous types of blue cheese include Roquefort from France, Gorgonzola from Italy, and Stilton from England. People often crumble blue cheese over salads, melt it into sauces, or serve it with fruit and nuts. The flavor is intense and salty, with a creamy, sometimes crumbly texture.

The same mold family used in blue cheese also produces the penicillin antibiotic that fights infections, though they're different species. Blue cheese definitely takes some getting used to: many adults acquire a taste for it over time, while others never warm up to its pungent flavor.