As visual representations of realities beyond themselves, symbols are among the most effective ways to communicate. Good symbols have a complex and psychological impact on people who see and use them. Baby harp seals and pink breast-cancer ribbons have generated widespread public acceptance for the causes associated with them; armbands associated with the Holocaust or classic news photos of 9/11 can evoke a powerful emotional response years after those events; and personal keepsakes from weddings, proms and special vacations summon up emotions over a lifetime.