Just to expand DIV, you can use following code:
$('.wrapper').find('a[href="#"]').on('click', function (e) {
e.preventDefault();
$(this).closest('.wrapper').find('.small').toggleClass('small big');
});
Where wrapper is used to let link being displayed
UPDATED code
To make it collapse too:
$('.wrapper').find('a[href="#"]').on('click', function (e) {
e.preventDefault();
this.expand = !this.expand;
$(this).text(this.expand?"Click to collapse":"Click to read more");
$(this).closest('.wrapper').find('.small, .big').toggleClass('small big');
});