No matter where the source of their DNA, as soon as the embryos became hollow balls of cells, between the developmental stages known as blastocyst and morula, telomerase lengthened telomeres to the right size. (sciencemag.org)
The Kibble Nibble is the easy, «beginner» version — basically an egg - shaped hollow ball with a small hole at each end. (drjensdogblog.com)
He is designing featherweight, grapefruit - size hollow balls that can be dropped from a spacecraft or balloon, charting storms and other weather patterns as they descend. (discovermagazine.com)