How we deciphered Ancient Egyptian hieroglyphs
In 1822, Jean-François Champollion found an essential clue from the newly discovered cartouche (oval rings enclosing certain groups of hieroglyphs, generally names and titles) containing the name of Cleopatra. The alphabet was now mostly correct and allowed him to translate the names of dozens of rulers.
When Tutankhamun's cartouche was discovered in 1922 and deciphered, it turned out that the "chick" pictogram was phonetic for the vowel 'u', the 'shepherd's crook' was a symbol meaning 'ruler. This was the turn of uncovering the secrets of a great civilisation.