THE WORLD OF INVISIBLE LIFE 
15 
white, or gray lines and dots, with only now 
and then a bit of green or red. Naturally, 
they are hard to see clearly. To make them 
much easier to see, we add a little specially pre¬ 
pared dye of red, blue, purple, or yellow, to the 
drop of water. Certain parts of the microbe 
will absorb the dye and take on a brilliant col¬ 
oring, though such a stain usually kills the 
little animal. If the drop of water contains 
several different kinds of microbes, we can dye 
them different colors, for it has been found 
that one kind of microbe will absorb only a 
certain color, while another type will absorb 
only some other color. For the same reason, 
we can even dye one part of a single microbe 
one color and another part a different color. Of 
course, this is a delicate process. It has taken 
many men years of work and study to perfect 
it, and only one who knows a great deal about 
it and is very skillful can do it. 
In order to study any one kind of microbe, 
it is necessary to separate it from the many oth¬ 
ers that are around it. Then one may study its 
How can we 
see invisible 
things? 
