A Wave of Division

What am I looking at?  

This is a fluorescent image of a fruit fly embryo – with the nuclei of the developing cells labeled in shades of purple to gold, and cell membrane markers labeled in gray. You can see cells in various stages of division, with cells that have already divided on the right (1), cells undergoing cell division in the center (2), and cells that have not yet divided on the left (3).

Biology in the background  

During development, fruit fly embryos undergo multiple waves of cell division, allowing them to grow and transform into adult flies. These waves can start anywhere in a larva, but the wave seen here started at the posterior (back) end (3), and is traveling to the anterior (front) end (1).

Interestingly, at this stage of development, these cells do not have the cell membranes that encapsulate adult cells, but if you look closely you can see the location of the proteins (shown in gray) that will eventually be essential for the formation of a cell membrane around each nucleus (shown in purple/gold). The soup of multiple nuclei sharing the cytoplasm is called syncytium. The early nuclear divisions are synchronous and extremely rapid, occurring about every eight minutes. From the moment of fertilization, it takes only one day for a larva to leave the eggshell.

A fruit fly embryo is about half a millimeter long, or roughly 6.5 times the width of a human hair.

Technique  

 This image was created using fluorescence microscopy.