2D array help

Hello. I’m expermimenting array in actionscript 3.
The following 1-D array has no problem:

var item:Array = new Array();
item[0] = "10";
trace(item[0])

However, the same structure doesn’t work on 2-D array:

var item:Array = new Array();
item[0][0] = "10";
trace(item[0][0]);

What did i do wrong? :cry3: