Apply tool tip to grid cells , Extjs

To apply tool tip to grid cells first create renderer and set metadata.tdAttr to 'data-qtip='"your value "; i.e. as given below :

 renderer: function (value,metadata, record, rowIndex) 

{
              metadata.tdAttr = 'data-qtip="' + value + '"';

             return value;
}

and that's it :)