 Imagine using light to treat cancer, skin conditions, or even as an antiseptic. This idea is centuries old. In ancient Egypt, sunlight and plant extracts were used to treat skin depigmentation. Now this has re-emerged as a treatment called photodynamic therapy. The principle is simple. Use a non-toxic compound that accumulates in certain tissue types, such as tumor cells. If radiated tumor with light, which would activate those molecules that are now present in it, and initiate a very specific cascade of events which will produce toxic compounds. Those toxic compounds will then go on to kill the cancer cells. Very selectively and with minimal damage to the surrounding tissue. Now as you can imagine, the success of this kind of treatment is very much dependent on this very important cascade. My project focuses at determining what factors affect the initiation and the propagation of this cascade. And more specifically, I look at a set of new structurally unique molecules in order to be able to tell how changing their chemical structure will affect those properties I'm interested in. Now to be able to do that, I need to observe this cascade as it occurs in its own time scales. It is a little bit tricky, as it's incredibly fast. It occurs on what we call a femtosecond time scale. Now a femtosecond. That doesn't tell you much, does it? And even if I tell you that a femtosecond is 10 to the negative 15th of a second, you'll think that's a pretty small number, but it's a little bit hard to imagine. So I'll give you an example that first helped me understand exactly how small that is. One minute, and compare that one minute to the age of the universe. It will be the same as comparing one femtosecond to one minute. Incredibly fast, but we can observe those events. Using laser spectroscopy methods the same way as we use flash photography, we can use femtosecond laser pulses as our flashes of light to take snapshot of our molecules as they go through those events. Just like this photographer took an image of a golfer taking a swing. Using this method, I was able to show that by changing the chemical structure of my molecules, I can significantly affect this cascade. From increasing the amount of toxic compounds produced to completely the opposite and suppressing this cascade from occurring. Knowing the details of how the structure affects the function of my molecules, I can improve the way new and better photodynamic therapy agents are made. Thank you.