What would you play in the diagrammed position? If you said 10...Nde5! or 10...Nce5!, take full credit. White's position is already resignable after either knight move. White loses two pawns and is forced to move his king. Mega Database 2013 finds 18 games that reached the above position. In 15 of them, Black moved one of the knights to e5. He scored 14.5 points in those 15 games.
If you said anything other than 10...N(either)-e5!, please enroll in Remedial Chess Tactics 101 forthwith. But don't feel too bad: you're in good company. Garry Kasparov, arguably the greatest player of all time, also missed it. He played the lemon 10...Nb4?, which would have allowed White to survive after 11.Bd2! when White is only a little worse (-0.47 according to Komodo 9.02). Instead, White played 11.Bb1? and was steamrollered.
How long has the shot 10...Ne5! been known, you ask? For almost 90 years. It was first seen in Norman-Vidmar, Hastings 1925/26, which Black won in short order:
This trap was given in Irving Chernev's book Winning Chess Traps, first published in 1946. The entire game appears, for example, in Chernev and Reinfeld's The Fireside Book of Chess (1949), as well as in more recent works such as the Encyclopedia of Chess Miniatures (2014) and Müller and Knaak's 222 Opening Traps After 1.d4 (2008). It is scarcely believable that Kasparov did not know of this old chestnut. Even if he somehow did not, it is mind-blowing that so great a tactical genius could miss so obvious a shot.