Leto's revenge on Niobe is one of the most frequently retold cruelties in Greek myth, and it survives through several independent strands of evidence rather than one single source. The core story, that Niobe, queen of Thebes and proud mother of many children, boasted of her fertility above Leto's own two, provoking Apollo and Artemis to kill every one of Niobe's sons and daughters with their arrows, is referenced already in Homer's Iliad, where Achilles cites Niobe's grief to comfort the bereaved King Priam, showing the story was already familiar audience knowledge in the earliest surviving Greek epic. Later sources add that the grief-stricken Niobe was turned to stone, and ancient travelers, including the geographer Pausanias, identified an actual rock formation on Mount Sipylus in Lydia, in modern Turkey, as the petrified, eternally weeping Niobe, a natural feature whose water-streaked appearance was read by ancient viewers as the stone mother's endless tears.
The myth also left a lasting mark on Greek art: a celebrated group of large marble sculptures depicting the death of Niobe's children, known collectively as the Niobids and now held chiefly in the Uffizi Gallery in Florence, illustrates how central the subject became to Greek and Roman sculptors, and the story's popularity on painted pottery was significant enough that scholars have given the conventional name the Niobid Painter to an anonymous fifth century BCE Athenian vase painter identified purely by the distinctive Niobid scenes attributed to his workshop. Between a line in Homer, a mountain identified by ancient travelers, and a modern art-historical attribution built around the subject, few myths connected to Leto left as wide a trail of surviving evidence as her revenge on a boastful mother.