Dressed to Kill- Fibulae

"When he came back to Athens, bringing word of the calamity, the wives of those who had been sent out on the expedition took it sorely to heart that he alone should have survived the slaughter of all the rest;—they therefore crowded round the man, and struck him with the brooches by which their dresses were fastened each, as she struck, asking him where he had left her husband. And the man died in this way. The Athenians thought the deed of the women more horrible even than the fate of the troops; as however they did not know how else to punish them, they changed their dress and compelled them to wear the costume of the Ionians. Till this time the Athenian women had worn a Dorian dress, shaped nearly like that which prevails at Corinth. Henceforth they were made to wear the linen tunic, which does not require brooches."- Herodotus "The History"

Fibulae were brooches used by men and women to fasten their garments, from the Bronze Age to the Medieval era. The story as related by Herodotus tells of an incident in the Hellenistic age and explains (if somewhat anecdotally) the shift from the woolen peplos to the lighter linen or silk chiton. Fibulae seem to have started as straight pins, much like decorative hatpins today, and developed into a hinged accessory which is the ancestor of the modern safety pin.

Though the pins may initially have been used to hold garments together, they quickly became primarily decorative, worked in gold, enameled, painted, and engraved.

For anyone seeking a much more detailed article on fibulae I refer you to the font of all knowledge Wikipedia, which actually has a pretty extensive entry for the subject.