 Alright, so next let's talk about how to use the microscope and we're going to use a microscope slide called the color thread slide and as you can see this is just a glass slide and it has three small pieces of color thread placed on the slide and they're crossing one another and then there's a little round glass disc on top of the threads and that's called the cover slip. So the first thing we want to do is place the slide on the microscope. To do that we slide one of the stage clips back and slip the microscope so that it's completely cradled by the stage clips. Then what I'm going to do is manipulate the mechanical stage knobs which are on the other side of the microscope for view. I'm going to manipulate the mechanical stage knobs so that the colored threads are in the center of the circle of light coming through the stage. Then I'm going to look through the oculars and use the stage clips to make sure the threads are in the center of the field of view and I'm going to adjust the adjustment knob until the threads are clearly in focus. So now our threads are clearly in focus and we can see the intersection of the three colored threads on the microscope. Now suppose we wanted to look at the ends of the threads. We can do that by manipulating the mechanical stage knob to move the microscope slide around the stage. So here we have the end of the yellow thread and it's a little out of focus so I'm going to use the horse adjustment knob and then the fine adjustment knob to bring it into focus. Then we can move until we see the end of the red thread and we can move the slide using the mechanical stage knobs until we see the end of the blue thread. And suppose we want to look at the end of this blue thread on a higher power. So we will use our fingers and rotate the turrent or the revolving nosepiece until we feel the next power or the low power objective click in place. The low power objective has a magnifying power of 10x on this microscope. So I'll look through the oculars and I'll use the horse adjustment knob to get that thread into sharp focus. Now if you look at this thread closely you can see that this one thread is made up of many, many smaller threads and so this is a mono filament thread. This is made up of many smaller filaments. So perhaps we want to look at the end of this blue thread on an even higher power. Well the next highest power is called actually the high power objective and I want you to watch as I click this high power objective in place because you'll see that there's going to be very little space what we call a working distance between the high power objective and the specimen. Just a very small distance. Therefore we only want to use the fine adjustment knob to make adjustments to our working distance when we have the high power objective in place. Sometimes students will mistakenly use the course adjustment knob and they will move the stage so much that it hits the objective and that can break the slide and potentially damage the microscope. So it's very important to remember that we only use the fine adjustment knob when the high power objective is in place. Now we can see that our blue thread is made up of many smaller filaments. We saw that earlier but now we see that the filaments are magnified at a much greater power. I'm slowly rotating the fine adjustment knob and as I slowly rotate the fine adjustment knob you will notice that different filaments within the blue thread come into focus. This demonstrates what we refer to as depth of field. Even though those are very tiny threads they still exist in three dimensions and as I rotate the fine adjustment knob different portions of the thread are coming into view. So the microscope is a wonderful tool and it can last many years if it's taken care of and used appropriately.