A soldier fires a Carl Gustav recoilless rifle system during weapons practice in Helmand province, Afghanistan. Heavy weapons like these generate a shock wave that may cause brain injuries.
Sgt. Benjamin Tuck/CJSOTF-A/DVIDS
In a cluster of glowing human stem cells, one cell divides. The cell membrane is shown in purple, while DNA in the dividing nucleus is blue. The white fibers linking the nucleus are spindles, which aid in cell division.
Allen Institute for Cell Science