Where did those sparks come from?

Basically, all matter — whether it's a cloud in the sky or your hair — is made up of atoms. Atoms are very tiny particles — far too small for you to see unless you own a special scientific instrument. Atoms themselves are made up of even tinier parts. The basic particles that make up the core of an atom, or the nucleus, are protons and neutrons. Orbiting the nucleus are other particles, called electrons. Atoms can lose electrons or gain extra ones. When a surface or object has lost electrons, it's said to be positively charged. When it has an excess of electrons, it's negatively charged.

Electrons like for things to be in balance. They'll try to even out such imbalances by flowing from negatively charged surfaces to positive ones. When you slide the comb against your hair or the sweater, you're accumulating electrons on the comb. That static electricity is discharged when you touch the comb to the light bulb.