Theme Fit allows you to dynamically resize specific HTML elements with the aid of jQuery on the client side, aspect ratios maintained.
The elements to be resized (targets) as well as the elements which serve as size-reference (parents) are specified via jQuery Selectors. This allows you to shrink or grow practically any kind of HTML element (images, embeds, forms, etc.) to the size of another one, as long as the target is nested within the size-reference (parent) and the size-reference is a block-element.
Note that the resizing is happening with JavaScript on the client. It does not resize images in terms of data volume. Theme Fit's only purpose is to make HTML elements behave more flexible and to make the presentation-thing look better.