It's World Bee Day, and we're doffing our caps in thanks to the world's lesser known 'essential workers.' According to the UN, three out of four crops across the globe producing fruits or seeds for use as human food depend, at least in part, on bees and other pollinators. And tens of thousands of flowering plants, like the crocuses in today's photo, would not exist if it weren't for the little buzzers. A quote often misattributed to Albert Einstein suggests humans would have only four years left to live if the bees go extinct. No matter who said it, the message is clear: Our livelihood is intimately tied to the survival of bees. And that connection is of critical importance now, as bee colonies continue to struggle after more than 20 years of mass die-offs, a phenomenon known as colony collapse disorder.