The kiss is very stimulating to most people.    The lovers begin with lips closed, soft and warm. After some degree of excitement, kisses become    firmer, wetter, and faster.     The muscles of the face and the mouth, relaxed, contribute to a more intense and sensual contact.The man can stimulate the upper lip of the woman, by nibbling it and sucking it tenderly while she plays with his lower lip, using her teeth and tongue. These kinds of exchanges can lead to immense pleasure for both lovers.