How did I burn out this ESP8266 unit? ESP8266 -> FTDI -> USB Mac

I followed the wiring on this page: http://williamdurand.fr/2015/03/17/playing-with-a-esp8266-wifi-module/



I was communicating with it via Serial at 115200.  I issued a AT+UART_DEF=9600,8,1,0,0 and a few seconds later I looked over and it was smoking.



I bought 2 of these.  The previous one I had wired to an Arduino Nano running through a logic level converter.  That one only returns Exception (28) over and over again after issuing that same command.

On both units AT+GMR returned:

AT+GMR
AT version:0.40.0.0(Aug  8 2015 14:45:58)
SDK version:1.3.0


Are these units too hard to use? What did I do to burn it out?

[UPDATE]

Answer given was that I fed it 5v instead of 3.3v. Obvious. I didn't think I did but I checked the output of the FTDI and sure enough it was 5.1v.  So why does the output on it say 3V3 ?  I thought that meant that it was 3.3v...



Should have checked it first.
You supplied 5V to a device that only takes up to 3.6V. Heat generated by the excessive power did the rest.