The Atlantean Beehive is a great source of useful gifts and bonuses. You'll find it at the entrance of every Endless Island.

Where to get Nectar? 

Buy some nectar from the Trader and give it to the bees. You can buy up to 18 nectars on each Endless Island. 

How to paly the Beehive? 

Open the beehive and tap Start. The bees will take the nectar and reward you with one of the items in the honeycomb.