The word 瞬息万变 is formed by combining the two-character phrase 瞬息, which joins 瞬 (blink) and 息 (breath) to denote an extremely brief moment, with the two-character phrase 万变, which joins 万 (ten thousand) and 变 (change) to denote countless transformations; the entire compound literally means "in a blink, ten thousand changes" to describe rapid and frequent change.