Masterpiece

Leonardo da Vinci's Mona Lisa (c. 1503–06) is considered an archetypal masterpiece, although it was not produced for admission to a guild or academy.

A masterpiece, magnum opus (Latin for 'great work'), or chef-d'œuvre (French for 'master of work'; pl. chefs-d'œuvre; French: [ʃɛ.d‿œvʁ]) is a creation that has been given much critical praise, especially one that is considered the greatest work of a person's career or a work of outstanding creativity, skill, profundity, or workmanship.

Historically, a "masterpiece" was a work of a very high standard produced by an apprentice to obtain full membership, as a "master", of a craft guild or academy in various areas of the visual arts and crafts.