 So the theory for a perfect lens actually originated in about the 1960s, a guy called Victor Vecilago. He said that you could get something called a negative refractive index, which essentially means that when you look at a prism or something like that, light tends to bend a certain way. And he proposed that you could get light to bend the other way if you so wanted. And this is the basis point of perfect lens. Current limitations with optical microscopy are mainly due to something called the diffraction limit, which was divided by a guy called Ernst Ab in 1873. Now the problem with that is that light is a wave, and as a wave, it diffracts in certain ways. The fraction of it means that it can only resolve down to a very small spot, but a fixed size of spot. So you can get to about 200 nanometers across, and that's about, I'm talking, a millionths of a millimeter. And you can't go any further than that due to the wave-like nature of light. So that's a big problem. The refractive index of material is how much light slows down when it travels through such a material. So the light is travelling from air and into water. And when it hits the surface, it reflects a little bit, but it also transmits, and it bends at an angle that's related to the difference in refractive index between the two materials. Now water, and pretty much all materials in nature, have what's called a positive refractive index. So what's happening here is the light is going from air into water, and you can see that the light is bending towards the normal when it enters the more dense material, which is the T. If this wasn't T, but a negative refractive index material, something different would happen. The light wouldn't be on the left-hand side of the normal, it would instead be on the right, so light would come in this way, but then bend back on the opposite side to the surface normal. The actual idea for a perfect lens for it to be used to image things came up with a guy called Sir John Pendry in about late 1990s, and it was demonstrated in early 2000s. And this idea basically uses a metamaterial. So a material that's comprised of very small structures, much smaller than a wavelength of light. And by arranging those structures in certain ways, you can amplify light waves and get them to diffract the wrong way. And you can see images you wouldn't normally be able to see on a much smaller scale. With nanotechnology, you're dealing with things that you can't see. So it's really important that you have these tools that allow you to see a nanoparticle inside a cell that's really complex. So if you're doing bulk measurements just on a lab bench, it's difficult to interpret the results. And that's where microscopy and high-resolution optical microscopy and electron microscopy are so important. And more so now that we're dealing more with nanotechnology. So we look at the interface between nanotechnology and the immune cells using nanomaterials to try and control the responses where the body decides, the immune system decides whether it's going to attack an infection or a cancer or whether it's not going to. And the reason that's a nanotechnology or a nanoscale problem is because what these high-resolution microscopies are beginning to reveal is that there are a lot of exceedingly small structures, so down to the level of tens of nanometers or less. And these structures are critical to the way cells talk to each other. So when your immune system decides whether it's going to attack something, there are spatial structures at that size which are helping to mediate that decision. So the ability to image those is vital to understanding that. And it's also vital to understanding how to control that process if you want to for therapeutic reasons. In our group, we're interested in looking at the interaction between a cell and nanoparticles. And you can't currently see that in the conventional optical microscope. But if you could watch where an individual nanoparticle is interacting with the cell, what compartments it's going into, what effect it has on the cell structure, that would be really interesting to do in a live cell. And cells, when they're alive, they're generally quite transparent and colourless. So you'll have to stain them if you want to see them. And that is actually obviously influencing the cell itself. And you don't want to do that because then it starts messing with the processes. Not only are the imaging techniques coming online, but also nanotechnology techniques that enable us to build structures on the same size as these vital structures. I mean that we can interact directly with these vital features. We can help try to control their size or to pull them around or to position them. And so these two technologies coming in parallel should really show some exciting results. Perfect lensing principles have actually been demonstrated already on things like maybe 20, 30 nanometers, which is already a good 10 times below the diffraction limit. So we've shown that it works. It's just going to take a bit more time or maybe a little bit of someone's clever idea to make it actually a reality.