Welcome to the better side of 50.

This time of life is called the Third Age, meaning that the first 25 years were spent developing as a person, the second 25 dedicated to pursuing a career and raising a family, and the third 25 are a time of coming into one's own and examining creativity, continued learning and exploration.

Third Age as a concept challenges long-held myths and stereotypes that presume aging to be a downhill slide into all that is ill, limited, unwanted, misunderstood, supported by government and worse. The fact is that the mature years may well be the best, healthiest and — if you make it happen — the most productive of your life.

Research findings from federal and state agencies, educational institutions and the private sector also document that the myths and stereotypes are wrong.

Today's 70 million people age 50-plus are the healthiest mature adults in history, even though predecessors may have lived in times and locales free of pollution, with much lower stress levels and fewer diseases.

Life spans are longer than ever — today's 65-year-old may expect to live an additional 17 years — and scientists are now projecting that a 100-year average life span may be very possible if not yet totally predictable.

Eighty-five percent of Americans 65-plus report their health as being excellent to good, with 15 percent describing it as so-so to poor.

"The risk for health problems in aging, long considered as inevitable, are really preventable and, in many cases, reversible," says Shawn A. McGivney, New York-based geriatrician and founder of the Wellness Foundation. "Genetics affect only 30 percent of our personal health; while what we do in lifestyle and environment determines 70 percent of how we feel, look and can do in the mature years."

Only 3 percent of adults from 65 to 84 are in nursing homes; that increases to under 5 percent when 85-plus individuals are included.

"In fact, Americans on the whole are aging remarkably well. They are experiencing less disability, dementia and dependence than our worst fears led us to believe," write Dr. John W. Rowe, president of the Mount Sinai Hospital School of Medicine, and Robert L. Kahn, professor of psychology and public health at the University of Michigan, in their book, "Successful Aging."

Based on 10 years of multidisciplinary studies sponsored by the MacArthur Foundation, the findings show that regular exercise is the single most important factor in sustained health.

"Even the oldest-old can benefit from changes in lifestyle and habits. In one study, frail nursing home residents were able to improve their muscle strength and increase their walking speed by 50 percent with a light weight-training regiment," the two write.

Today's mature adults, 55 and over, control $1 trillion in spending each year, $160 billion of it in discretionary spending. Seventy-five percent own their homes, with 80 percent of those mortgage free. This age group also holds 70 percent of all funds in savings and loan institutions and has a net worth more than double that of younger adults. The statistics are reported from the U.S. Census Bureau and the U.S. Department of Health and Human Services.

More than just evidencing a life of positive accomplishment and saving, seniors comprise America's richest market, one yet to be discovered by many marketers, businesses and organizations.

"The market is here today and has been here for years," says Robert S. Menchin, Chicago-based author of "The Mature Market: A Strategic Guide to America's Fastest Growing Population Segment."

"The baby boomers will add to the mature population; but where else in today's marketplace can you find the financial ability, expanding interests and the time to do and enjoy what they want?"

Time, financial ability and personal growth and adventure provide opportunity for both the mature population and the businesses and organizations that serve them, Menchin says.

The time of maturity can be likened to the children's story "Pinocchio," when the puppet is transformed into a real boy. "Most mature adults discover that the controlling strings have been removed," says Mark Fagan, professor at Jacksonville State University in Alabama and a consultant on retirement issues.

"Children have already left the nest so mature adults can chart their own paths forward. Many times this means a move to a better lifestyle, safer community or somewhere they can be involved. We have seen a remarkable in-migration to cities and towns throughout the South."

Unlike the stereotypes that depict older adults as technophobes — unable to cope with high-tech anything — today's mature adults are the fastest-growing demographic group buying computers and signing onto the Internet.

"Already, 7.6 million Internet users are age 50 or better," says Mary Furlong, professor of education at the University of San Francisco, and founder of the SeniorNet nonprofit and ThirdAge commercial Web sites. "Age 50-plus Internet users also spend more time online per session than their younger counterparts."

A study sponsored by SeniorNet documented that mature adults spent an average of 12 hours per week using computers, compared with male adults and college students at nine each, female adults and teenagers at seven hours each, and children under 13 at five hours.