Today's youth is typically portrayed with a veneer of deadpan detachment; the visual equivalent of a hoodie. In contrast, the 19 subjects of Emma Hardy's small exhibition, Exceptional Youth, are passionate, determined and obsessed (with sport, music, inventing, campaigning).

Apart from the precocious stars, Daniel (17, Harry Potter) Radcliffe, Lily Cole (18, model and charity ambassador) and Theo Walcott (17, Arsenal star), most are unknown, and most defeated extreme challenges, some from birth (the cerebral palsy of cherubic singer Blaine Harrison, 21, the spina bifida of Paralympic dressage champion Sophie Christiansen, 18, standing by her horse). But, like her subjects, Hardy avoids sentimentality and heroism in her presentation of quiet maturity.

In the Face of History
Barbican Gallery
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Similarly, the struggle for survival (on a personal and social scale) dominates the Barbican's magnificent sweep through 20thcentury European photography by 22 artists. It is arranged into eras largely defined by war and revolution (Marxist to Sexual).

Opening with the pioneering Eugene Atget's artful scenes of Parisian artisans and alleys, and Brassai's defining and risqué look at brothels and bars, it includes André Kertesz's moving records of soldiers during the Austro-Hungarian war (1914), and the astonishing experimental portraits of Poland's Stanislaw Ignacy Witkiezicz (Witkacy).

Powerful records of the Holocaust include Henryk Ross's potently mundane methods of survival in the Lodz Jewish Ghetto in Poland, while the social impact of the Cold War similarly inspired Ukraine ' s Boris Mikhailov.

His photo-essay, Red, a vast, popart parody of Soviet poster art, contrasts with the grim realism of his small vignettes of struggling people in bleak streets. A generation away, Wolfgang Tillmans's Polish Market (Berlin) resembles a dishevelled school project.

The challenges of the sexual revolution and our obsession with personal identity are recorded in Christer Stromholm's sensual Fifties portraits of Stockholm's first transsexuals, Aders Peterssen's sensitive character studies of Sixties Hamburg junkies and prostitutes and Ed van der Elsken's humorous look at Holland's Seventies hippy politics and miniskirts.

In contrast, Selichi Furuya's personal quest for meaning through obsessive explorations of his late wife's face is a claustrophobic, provocative ending to this exhilarating representation of the century's personal challenges.

• Exceptional Youth: Photographs by Emma Hardy, until 8 April. 020 7306 0055. www.npg.org

• In the Face of History: European Photographers in the 20th Century, until 28 January. 0845 120 7550. www.barbican.org.uk