Nests are items that allow Keepers to track their Peridots once they have been released. Giving your Dot a Nest gives you the ability to swap back to it at any time. There are a limited number of slots available for Dots with Nests in your inventory, but you can purchase Nests in the store to unlock more slots.

To view your Dots tracked with Nests, tap on your backpack and select the Journal. Tap on any Dot to swap to it.