At left, a woman holds the saffron crocus during the saffron harvest in Herat, Afghanistan. At right, saffron flowers are collected in Saint Hippolyte, eastern France. Since the stigmas need to be picked from the flowers by hand, saffron is the world's most expensive spice. Majid Saeedi/Getty Images; Maxppp /Landov hide caption

toggle caption Majid Saeedi/Getty Images; Maxppp /Landov

The orchids that produce vanilla beans have no natural pollinators in Madagascar; the plant must be pollinated by hand — a labor-intensive process with little margin for error. Courtesy of Madécasse hide caption

toggle caption Courtesy of Madécasse