When you buy or cook a steak, the white lines you see inside the meat are called marbling. Knowing how marbling works can help you pick a steak that tastes better and feels juicier.

Marbling is intramuscular fat that appears as thin white streaks woven through the lean muscle. This fat plays a major role in how a steak tastes and feels when it is cooked.

When beef is seared at high heat, the intramuscular fat melts and spreads flavor compounds through the muscle fibers. The melt creates a richer, more savory taste than very lean meat. The melted fat also coats the mouth, making the steak feel juicier than the meat’s own juices.

There are three common marbling patterns. Level 1, called Stardust, has small scattered dots of fat, is relatively lean and usually cheaper. Level 2, called Fine network, shows thin streaks that give a good balance of tenderness, juiciness and rich flavor. Level 3, called Snowflake, is dense and even, like the A5 Wagyu pattern, and gives an exceptionally tender and rich steak.

Chef Vu Nhat Thong says shoppers should look for even distribution of marbling. A cut with fine, evenly woven fat usually cooks more evenly and gives better flavor and tenderness than a leaner cut with a large pocket of external fat.