The Hubsan X4's Flight Controller (aka Control Board) has a handful of neat components that keep the quadcopter in the air:

Hubsan HBS002 Processor

Invensense ITG-3050 Integrated Triple-Axis Gyroscope

16.000 MHz Quartz Crystal Oscillator

3210AP 3-Axis Accelerometer

A7105 2.4GHz Wireless Module