Arduino Communication Project

I am trying to have two arduinos talk to each other using an xbee rf modules. And i need the arduino boards or at least one of them to be as small as possible. What are the smallest boards that are compatible with the xbee module?

What flavour of xbee as there are several variations.

If you want small then xbee is maybe not ideal as the standard form factor they come in is quite large.

Possible alternative options could be something like Moteino or ESP8266.

Another very cheap (and effective) option is the nRF24l01+ transceiver.

...R Simple nRF24L01+ Tutorial