Are you a Higgs boson?

[arianayaris]

Are you a microscopic particle? (http://en.wikipedia.org/wiki/Particle#Size)

Would your name be recognizable by a layperson with no degree in the sciences?

[coolcat59]

Are you an object in the gaseous state?

[Shardz]

Are you a snowflake?

Is the host of this round ( ) more concerned with your specific properties, uses and/or effects rather than your exact form (atom, molecule, etc.)?

[avoran]

Are you smaller than an individual atom?

BTW if anybody is interested in a separate Who am I? contest, please comment here

[nyuboy11]

Can any1 play?

Are you considered valuable (in terms of money)?

[agamal007]

Are you water molecule (H2O molecule)?

Are you an element?

[avoran]

are you a pollutant/health hazard?

[Fatima99]

star dust ?

Are you Carbon-14?

[Pericles]

Are you a quark