Dr. T. Charles John Bhaskar

Nitogen fixation is a process by which the inert nitrogen in the diatomic state is converted to forms of soluble nitrogen compounds such as ammonia or nitrite or nitrate which can be utilized by the plants. It can be a chemical or biological process.
Usually by lightening nitrogen is converted into nitrogen oxides which dissolve in rainwater and reach the soil. It will be converted into nitrites or nitrates by reaction with minerals such as calcium or magnesium. It is a chemical fixation. It can also be fixed by some bacteria called nitrogen-fixing bacteria or blue-green algae.
Nitogen fixing bacteria can be free-living as in the case of Azotobacter or Rhodospirillum, or it can be symbiotic in root nodules of legume plants such as Rhizobium. The latter type of nitrogen fixation is called biological nitrogen fixation.
It is a shorter answer. The process is relatively complex and is beyond the scope of this section.

Fullerenes are allotrophs of carbon as mentioned by many others. Compared to the other allotrophs like graphite or diamond, it forms a three-dimensional structure consisting of a five or six-membered rings.
Still, some have not mentioned that it is just a unit that can make the ball like structure called Buckyballs or Fullerene named after the architect, Buckminster Fuller who made a geodesic structure made with 60 joints.
The simplest fullerene can have C20 (twenty carbon structure), and the structures can vary by the number of carbon atoms such as C60, C80, C180, C240, etc., Similar to the cage or ball-like structures one can find "bucky tubes" too which are cylindrical.