Capsicum
The heat in peppers is due to the chemical capsaicin (Isn't that the name of a muscle pain cream? Yes, and don't eat it.) During the growth of the pepper pod, capsaicin travels along the membrane of the pod. Depending on the age and/or maturity of the pepper pod, capsaicin traces may not have been absorbed completely into the walls (skin) of the pod. This means you could take a bite into a habanero and taste a sweet/fruity pepper. Take a bite into the vein of the pepper and get ready to drink the water. The seeds of the pepper do absorb capsaicin. Just like the skin of the pepper, maturity of the pod does influence how much capsaicin is absorbed into the seeds.