2. A child who reaches age 21 without smoking, abusing alcohol or using drugs is virtually certain never to do so. -Joseph A. Califano, Jr., Chairman and President, -The National Center on Addiction and Substance Abuse at Columbia University

4. Alcohol no alcohol one year later

5. Sandra Brown and Susan Tapert, clinical psychologists at the University of California, San Diego, and at the Veterans Affairs Medical Center there, found that 15-to-16-year-olds who said they had been drunk at least 100 times performed significantly more poorly than their matched non-drinking peers on tests of verbal and nonverbal memory. Susan Tapert/University of California, San Diego The images above show the brain activity of a 15-year-old nondrinker, top, and a drinker, bottom. The teenagers, who were sober during the testing, had been drunk an average of 750 times in the course of their young lives.

6. A time-lapse 3-D movie that compresses 15 years of human brain maturation, ages 5 to 20, into seconds shows gray matter - the working tissue of the brain's cortex - diminishing in a back-to-front wave, likely reflecting the pruning of unused neuronal connections during the teen years. Cortex areas can be seen maturing at ages in which relevant cognitive and functional developmental milestones occur.