Retina Display

• The fourth generation iPod Touch is the first Touch device to feature Apple's Retina display. The most significant feature of the new display is a higher resolution than other iPod touch models. The resolution was increased from 480 by 320 pixels on previous models to 960 by 640 pixels. The Retina display is accompanied by a touch-sensitive digitizer that can detect up to 10 points of simultaneous contact at any one time.
  
  

Cameras

• The fourth generation iPod touch is the first model to feature built-in digital cameras. The device has a rear-facing camera capable of capturing video as well as photos and recording in high definition at 720p resolution and at 30 frames per second. The forward-facing camera is used for Internet-based video calling through applications such as FaceTime and Skype. This is also the first model to feature a built-in microphone, though it's also able to accept an external microphone through the headphone socket.
  
  

Size

• The fourth generation iPod touch is the thinnest Touch model, measuring 4.4 by 2.3 by 0.28 inches, which reduces the device's depth from 0.33 inches on the previous models. It's weight has also been reduced from 4.05 ounces on the previous generations to 3.6 ounces. Despite the increase in pixel density, the physical screen size remains consistent with previous models of the iPod touch and with the iPhone, at 3.5-inches measured across the diagonal.
  
  

Controls

• Motion sensing is built into the device through the inclusion of a three-axis accelerometer, though the fourth generation iPod touch is the first model to also incorporate a gyroscope for angular movement detection and acceleration. The touchscreen provides the device's primary form of user input, accompanied by the physical home button for closing applications and volume controls on the side of the casing.