If you're interested in this sort of thing, there is a great class at RPI which has its lecture slides available:

http://security.cs.rpi.edu/courses/hwre-spring2014/

The slides for lecture 4 (http://security.cs.rpi.edu/courses/hwre-spring2014/Lecture4_...) shows what various types of components (such as laser-trimmed resistors) look like on a die.