When Ellen Key proclaimed this the Century of the Child sixty years ago, she might better have called it the Century of Adolescence. The modern dimensions of childhood had been developing steadily during the course of the nineteenth century. Adolescence, on the other hand, previously characteristic only of those privileged youngsters who were exempt from early entry into the job market, was beginning in 1900 to involve a much larger part of the population. Laws were excluding the teen aged from the job market and simultaneously cloistering them in the expanding sector of secondary education. Coincidentally, a whole set of extracurricular organizations, including sports clubs, youth hostels, and other age-graded activities, came into existence. Two of these, the German Wandervogel and the English Boy Scouts, the former founded in 1901 and the latter seven years later, were to become symbols of the era of adolescence in European history, a period whose distinctive social, political and psychological dimensions are the subject here.