How did Hank figure out Walt is Heisenberg?

Related questions

1. What happened to Malcolm's father?
2. How did Jesse Pinkman girlfriend die?
3. Did Walt die at the end of Breaking Bad?
4. Why was breaking bad Cancelled?
5. Does Walter White come back in better call Saul?
6. Does Hank find out about Walt?
7. Will there be another breaking bad series?
8. How old is Reese from Malcolm in the Middle?
9. Is there a breaking bad season 6?

Tags

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2. #favorite
3. #final
4. #murder
5. #libertarian
6. #leaves
7. #scene
8. #hapless
9. #vegan
10. #other
11. #conspired
12. #working
13. #heisenberg
14. #figures
15. #season
16. #toilet
17. #perusing
18. #jesse
19. #inscribed
20. #boetticher
21. #chemist
22. #grass
23. #while