Rain water runs over the land and collects in lakes or rivers, which take it back to the sea. The cycle starts all over again. Image caption ... is required to view this activity.

This image shows the replication cycle of HIV/SIV. The virus replicates in the body's own CD4+ T helper cells. In doing so, it introduces its own genetic information into the DNA of the host cell.

Summary image of the article. The upper part highlights neuronal cell cycle re-engagement is a stage proceeding neuronal senescence and that their full molecular profiles can now be identified by ...