It's actually the expanding debris from a star first seen in 1572 by astronomer Tycho Brahe. This image was taken by the Chandra X-Ray Observatory, and shows very high-energy X-rays in blue, and lower energy X-rays in red (both have been superposed on a sky survey image of stars representing the location of the nebula). The initial blast wave from the supernova is slamming into gas around it, compressing it, heating it, and generating crazy strong and chaotic magnetic fields. These fields accelerate electrons to super high velocities, making the X-rays shown in blue. The X-rays shown in red are from the supernova material itself - the outer layers of the star expanding outward behind the shock wave.
These Chandra observations showed that expanding debris from a supernova can accelerate subatomic particles faster than previously thought, and in fact can account for the highest-energy protons that come from outer space and are seen hitting the Earth's upper atmosphere. It had long been suspected this was the case, but these data provided pretty strong evidence this was the case. In fact, just before posting this Top Pictures list, a NASA press release came out saying the Fermi satellite has seen gamma rays from this object, which is another very strong piece of evidence for this; gamma rays are the very highest energy form of light, and should be made when subatomic particles bounce around in supernova shock waves.
So while the Tycho supernova remnant may look like some sort of blastocyte, it's really a blast site. Ironically, supernovae make heavy elements that get dispersed into space, which eventually form stars and planets... and life. So maybe "blastocyte" isn't too far off.