I'm going to take you on a journey into some hidden worlds inside your own body using the scanning electron microscope. These microscopes use a beam（梁） of electrons to illuminate things that are too small to be seen by the photons of visible（可见的） light. And to put this in context if you mentally divide one tiny millimeter（(millimetre)毫米） into a thousand parts each one of those parts is a micrometer or micron（微米（等于百万分之一米）） for short. If you then divide one micron into another thousand parts each one of those is a nanometer and it's nanometers and microns that are the domain（领土） of the scanning electron microscope. So let's start with something on the body that we can measure at about 100 microns wide and that would be a human hair which now you can see is covered with scales（刻度） just like all of our hairs and in fact just like all mammal（哺乳动物） hairs. We're going to plunge（使投入） into the body now and we've landed in the thyroid gland（[解剖]腺）.

  Here we're looking at proteins（蛋白质） that are being secreted（隐秘） into a storage（贮藏） chamber where they're going to develop into the mature thyroid hormones before being released into the body. And at this point you might be wondering if these colors are real. The answer is no. Electron images only happen in black and white. I often colorize my images for various reasons but I don't change the structures. So the structures that you're seeing are all exactly as they were when I photographed them in the microscope.

  We're going to take a detour and zoom in on the heart muscle now and the heart muscle has this curious（好奇的） structure that's kind of like corrugated cardboard（[纸] 硬纸板）. That's what allows the heart to expand and contract（收缩） as it's beating. Let's go look at a lung（肺） with pneumonia（[医] 肺炎）.