How can a metal-oxide-semiconductor (MOS) transistor suffered from multiple dielectric breakdowns with severe structural damages (e.g., local melting and metal migration) remain functional? In this talk, I would share with you various breakdown related defects in nanoscale transistors used in state-of-the-art computer chips and mobile devices. It is amazing to realize that even a transistor has suffered a catastrophic failure, it can still be functional with degraded performance. I will show the first time a real-time physical analysis of a breakdown in an ultrathin dielectric of less than a few nanometers (1 nm = 10-9 m).