An extension tube reduces minimum focus distances, and increases the lens maximum magnification, enabling for greater close-up photos
BRIAN SAYS… Macro photos larger than life-size are the realm of the specialist lens or some add-ons to yourlenses. You can add a Canon close-up lens (looks like a filter) to your current macro lens which acts like a magnifying glass and attaches to the lens filter thread, but as they are optical elements they can be pricey. Another choice is to use an extension tube, this moves the lens away from the sensor and so allows it to focus closer but at the expense of being able to focus on infinity. Extension tubes are generally inexpensive and a 25mm tube should give your 90mm lens almost 1.4x magnification. There are also reversing rings to mount old manual focus lenses in reverse. This is the least expensive choice, but magnification is less than extension tubes and close-up lenses.