Mahadevan and Liang created a time-lapse video of the blooming lily over the course of 4.5 days, taking one photo every minute. Over the first 4 days, the bud grows 10 percent longer and 20 percent wider. Hidden from view, though, rapid growth at the edges of the petals is creating stress that will soon force the bud to burst open. After 4 days, the hidden petals already have ruffled edges. When the growth strain reaches a critical point, the flower blooms.