Prior to its release, the album's working title had been "That Chick", which was also the working title of a song on the album that would eventually be titled, "I'm That Chick". As the release date drew near, the title was changed to "E=MC²", in reference to Carey's previous album, "The Emancipation of Mimi" (2005). The title signifies "(E) Emancipation (=) of (MC) Mariah Carey (²) to the second power". It is a word play on Albert Einstein's famous mass–energy equivalence formula and has been dubbed as the sequel and improved counterpart to "The Emancipation of Mimi". In his review of the album, Alex Macpherson from "The Guardian" described his thoughts on its title, as well as its meaning: