On a microscope, the iris diaphragm controls the amount of light.
Zacharias Janssen
You place your slide on the stage of a microscope.
100x with oil immersion
Anton Van Leewenhoek
telescope, micrscope, barometer and thermometer
It's big under the micrscope
it is called the diaphram.
The diaphragm is not made out of bone, but the diaphragm is a muscle.
The muscle you are referring to is the diaphragm. It also separates the thoracic cavity from the abdominopelvic cavity.
The distance in front of and behind the focal point that is in relative focus
antonie van leeuwenhoek
the diaphragm is the muscle separating the chest and the abdomen