This subject is a common fruit fly, as seen through a 100X microscope. Individual image on the left, stacked result on the right.

Why use it?
Zerene Stacker has several advantages over other commonly used stacking programs:
Highest quality output images, especially in difficult cases
Accurate and robust alignment and interpolation
Advanced stacking algorithms
Clean handling of hairs and bristles – no halos or contour lines
Preserves low contrast detail and avoids “stacking mush” with deep stacks
Fast and flexible retouching makes it easy to combine the best features of multiple algorithms as well as original frames
Retouching supported by all versions, even at the lowest price
Supports 8- and 16-bit input and output files
Can generate stereo and 3-D rocking animations from a single stack, even for difficult subjects with structural overlaps and bristles.
Fully utilizes modern multi-core processors and multi-processor computers