To view data and make it easier for scientists to study the experiment
The best answer that is being described above is the RODS. Along with cones, Rods are one of the photo<span>receptor cells in the retina of the </span>eye. Unlike the cones that help with color vision, the rods focuses more on the gray scale, the reason why we can see everything in a gray scale at night or in a dark environment. Hope this helps.
<span>the high expense; electron microscopes are costly</span>
I believe that would be irritability.