Crysis 2

Tip for anyone that may experience what I did when killing the alien. There was no icon telling me to take the tissue sample once the alien had died. I restarted the checkpoint 3 times and there was still no message instructing me what to do. If this happens to you just walk up to the dead alien and hold X on his corpse and the achievement should unlock. There is supposed to be an icon telling you to hold X, which I saw in a walkthrough video. Even if you do not get the message holding X will still work to take the tissue sample.

If like me you prefer a more visual solution see below;


I take absolutely no credit for the making or production video, just showing you where it is ;)