Michio Hanamizu has served countless cups of tea since he started managing a tea farm 15 years ago, but one tasting was especially memorable. Compared with his usual prospective customers, this time it was particularly challenging to impress the participants’ palates: They were preschool students.

Hanamizu brewed a few different teas for the children, who were sampling them as part of an early childhood education program, and something unexpected delighted them.

“It seemed like the kids were not interested in green tea,” Hanamizu recalls. “But when we brewed black tea for them, their eyes shined.”