Which rule was recently introduced/modified in chess officially? Chess has lot of interesting rules such as castling, en passant, 50 move rule, stalemate, etc.  I am interested in knowing the history behind the introduction of chess rules.

Can anybody explain which rule was recently introduced/modified in chess officially?
Do you mean what rules have been changed the most recently? FIDE, the international federation of chess, just changed some rules four days ago (2014 July 1). Changes include:


You are now officially allowed to promote a pawn by removing it from the board while it is still on the 7th rank and then placing a new piece on the 8th rank, rather than moving the pawn to the 8th rank and then removing it. You may also place the new piece before removing the pawn. (The move has not changed, just the list of allowable ways of executing it.)
If 75 consecutive moves have been played without a pawn move or a capture, or the same position has occurred for 5 consecutive alternate moves in a row, the arbiter is allowed to step in and declare the game drawn (without a player claiming a draw).
Players may not bring cell phones into the tournament hall at all.