The NodeMCU is an open-source firmware and development kit that helps you to prototype your IoT (Internet of Things) products within a few lines of Arduino code or Lua script.
This is the latest version: 2nd generation. For use with an Expansion board its footprint base width is 24 mm. appx.
Its Low cost, Simple, Smart, WI-FI enabled. It has a 32-bit, 80MHz CPU, 64KB of RAM and 4M byte of flash memory on board. Compared with a standard Arduino (8-bit, 16MHz, 2.5KB RAM and 32KB
(NodeMCU 0.9.6 build 20150704 powered by Lua 5.1.4)
What you will receive:
1 x NodeMCU devkit 1.0 ESP8266 12E