Plus has teamed up with the Royal Society Summer Science Exhibition 2011 to reveal the maths behind some of the science on show. We have chosen two exhibits from this year's participants and produced postcards for people to pick up at the stand, accopmanied by Plus articles to reveal some of the the maths behind them. Read the articles and if you can't make it to the exhibition yourself, you can also download pdfs of the postcards.

How would it feel to look in a mirror and see not your own reflection but instead how you would look as the opposite sex? You can explore this strange alternate reality at this year's Royal Society Summer Exhibition where scientists from Queen Mary, University of London and University College London will use mathematical wizardry to produce gender reversed images of faces.

Airport security staff have a daunting task. With impatient queues looming over them they need to search x-ray scans of cluttered suitcases for several items at once: knives, guns and bombs. How can we ease their task and make sure they don't miss a crucial item? To find out, scientists are trying to understand how we humans take in visual information. The humble triangle plays a crucial role in the experiments they perform.

Foraging ants have a hard life, embarking on long and arduous trips several times a day, until they drop dead from exhaustion. The trips are not just long, they also follow complex zig-zag paths. So how do ants manage to find their way back home? And how do they manage to do so along a straight line? Their secret lies in a little geometry.

When insects go foraging, they zoom off from their nest in complex zig-zag paths. How do they manage to find their way back home? And how do they manage to do so along a straight path? These questions are explored in an exhibit at the Royal Society Summer Science Exhibition, currently taking place at the Southbank Centre in London.

Water is essential for life on Earth, and it is a resource we all take for granted. Yet it has many surprising properties that have baffled scientists for centuries. Seemingly simple ideas such as how water freezes are not understood because of water's unique properties. Now scientists are utilising increased computer power and novel algorithms to accurately simulate the properties of water on the nanoscale, allowing complex structures of hundreds or thousands of molecules to be seen and understood.

People have been using gold particles dispersed in water — gold hydrosols — for medical purposes for over 1000 years. Recently, hydrosols containing gold nanoparticles have become particularly popular because they have exciting potential in cancer therapies, pregnancy tests and blood sugar monitoring.

Obesity has reached epidemic proportions and the World Health Organisation estimates that, by 2015, about 3 billion adults will be overweight or obese worldwide. These individuals will be at increased risk of cardiovascular disease, type 2 diabetes, cancer and osteoarthritis.