Lightest by Weight:
* A single atom would be the lightest object by weight. Atoms are incredibly tiny and have very little mass.
* A photon is a particle of light and is often considered massless.
Lightest by Density:
* Aerogel is a material with incredibly low density. It's so light that it can be held on a dandelion.
* Vacuum is technically the lightest thing in terms of density because it contains no matter at all.
Lightest in terms of Perception:
* A feather or a piece of paper are often perceived as being light because they are easy to lift and have a low density.
Let me know if you'd like more detail on any of these examples!
