The cell cycle has been the subject of intense investigation during two periods since Virchow's 1855 realization that cells only arise from pre-existing cells. At the turn of the century ...

Originally, cell cycle studies were the preserve of microscopy ... to the potential for disease and injury repair via stem cell therapies. Image: Steve Gschmeissner/Science Source.

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.