Sunblocks generally work in two basic categories. They're reflective or absorbent. The reflective ones basically look to bounce the sun's rays away. So that's what the zincs and the titanium oxides do—they're reflective sunblocks. Their trade-off is that they're a bit gluggy. They block the pores on the skin. That's what you see the cricketers wear—you've heard of the zinc and various other things. But that's their mechanism of action—they're reflective. They bounce the sun's rays away. The others are absorptive, and what they do is they absorb the sun and use the energy of the sun to break chemical bonds and form two, three, or four inert chemicals. I know that at one point in time, there was some concern around whether those inert chemicals could themselves be troublesome, but that hasn't proven to be so. I'm talking about things like PABAs, the para-aminobenzoic acids, and those sorts of things. They were very, very common in the early years for sunblocks and even today you'll still see them.