and the late Robert Allen 
of Dartmouth College 
began using video cameras 
to study living cells. 
Unlike the eye, a video 
camera can enhance an 
image to “see’' objects 
clearly even when the 
contrast between subject 
and background is very 
poor. Inoue and Allen 
used video cameras to 
watch food-containing 
sacs and other structures 
in the cell move rapidly 
along slender, track-like 
organelles. Video images 
can now be further 
enhanced by digitizing 
computers, which, when 
attached to a video 
camera, scan the cell, 
break down the image 
into light and dark bits, 
and then reconstruct the 
image so that “visual 
noise” (grayness) is sub- 
tracted, while objects of 
interest are highlighted. 
Another type of micro- 
scope, called the confocal 
microscope, is having a 
great impact on the 
study of cell structure. A 
confocal microscope 
passes a beam of light 
over a tiny portion of a 
cell, then focuses the 
light that reflects off the 
specimen through a pin- 
hole. A sharply focused, 
three-dimensional image 
of a cell or cell structure 
can be built up by 
recording the intensity of 
the light beam coming 
off each scanned point 
and then reconstructing 
the whole image on a 
viewing screen. Because 
confocal microscopes can 
be used on living cells, 
they allow researchers to 
watch cell movements 
and the interactions of 
neighboring cells. 
