What's Raisin Bran Effect?

A healthy breakfast won't just make you feel wholesome and energetic, it may also improve your understanding of the dynamic of particle based-fluids.

Named after the famed breakfast cereal, the raisin bran effect (officially known as granular convection) describes a seemingly gravity-defying phenomenon: when a mixture of variously sized particles was given sufficient amount of agitation, the larger and heavier ones always end up on the top layer.

Although there have been a few postulated explanations behind this phenomenon, it is generally accepted that the articles, embodied by the shaken cereal mix, can form convection cells similar to the dynamics of fluids. Both small and large particles follow the convection flow at the beginning. However, the latter become stuck on the top layer due to their size. Over time, the larger particle rises in the mixture. 

Source: It's Okay to Be Smart via Youtube