This is PG5. Its a synthetic molecule created by Dieter Schlüter with the help of other scientists at the Swiss Federal Institute of technology in Zurich. It amasses 200 million hydrogen atoms, and its the world's largest synthetic molecule.

The significance of it? Delivering targeted medicines into the human body.

Using what Klaus Mullen of the Max Planck Institute for Polymer Research in Mainz, Germany calls an "outrageous trick," the PG5 creators did a number of things that I don't quite understand just yet:
To synthesise PG5, Schlüter combined standard polymerisation reactions, which assemble small molecules into a long chain or backbone, with reactions from other areas of organic chemistry which attached groups of atoms to the backbone in a radial fashion. Schlüter says that because both techniques are standard, his team's work should encourage other researchers to create synthetic macromolecules that they were previously "not brave enough" to attempt.
More reading over at [New Scientist]