A Brazil nut is a large, rich-tasting nut that grows in the rainforests of South America, particularly in Brazil. These nuts come from massive trees that can live for 500 years and grow as tall as an 18-story building. The nuts grow inside hard, round pods about the size of a softball, with each pod containing 10 to 25 tightly packed nuts arranged like orange segments.

Brazil nuts have hard, dark brown shells that are notoriously difficult to crack, much tougher than walnuts or pecans. Inside is a creamy white nut with a distinctive, slightly sweet flavor. They're highly nutritious and packed with selenium, a mineral your body needs in small amounts.

You'll often find Brazil nuts mixed in with other nuts during the holidays. If you've ever noticed that the biggest nuts in a mixed nut bowl can seem to rise to the top when you shake it, you've observed something scientists call the Brazil nut effect. This happens because when you shake a container of different-sized objects, the larger ones work their way upward while smaller ones filter down to fill the spaces below. Scientists study this effect to understand how particles of different sizes behave when mixed together, which matters in everything from manufacturing cereal to designing pharmaceutical pills.