Has anyone done investigation into which components are still 'alive' during the sleep ? This can be done with an infrared camera, should be able to see which

Has anyone done investigation into which components are still 'alive' during the sleep ? This can be done with an infrared camera, should be able to see which components remain hot after a long period of 'sleep', or a voltmeter for the more electrically inclined. My bet is that its some kind of bus that isnt powering down and continually waking up the devices on it.