The stage should be as high as possible before you crouch
down and look through the microscope, and you should start
focusing by moving the stage down.
If you did it the other way, and started out moving the stage UP,
then you would run the risk of going too far without noticing it,
and smooshing the slimy bacteria all over the objective lens.
Then nobody could use that microscope until it came back from
the lens-cleaning shop, and what is worse, you might even have to
pay for the cleaning.
