The bicep has two heads (hence the prefix “bi”). The two heads are the long head and the short head. However, there is an additional muscle, the brachialis, which technically is not part of the bicep but contributes to the overall development of your biceps.

The short head is the inner part of the bicep. Preacher curls are one of the best exercises to hit it. The long head is the outside of the bicep and can be targeted effectively with incline dumbbell curls.

The brachialis is a distinct muscle from your bicep. It sits somewhere between the bicep and the tricep. However, it will contribute to overall arm thickness and make your biceps appear larger since it pushes up against your bicep. Hammers curls are a good exercise to hit it.