What Is An Atom And How Do We Know?

Ever wonder how we actually know that atoms exist? Here we'll learn what atoms are and exactly how scientists went about figuring all of this out.

Subjects: Chemistry


Atoms are the fundamental subjects studied in chemistry. Here you will learn the history of their discovery starting with the philosophical concept of atoms in ancient India and Greece. You will learn of experiments conducted by Islamic and European scientists which eventually lead to the formal description of atoms in 1808. Finally, you will learn of advancements in microscopes allowing us to actually see atoms with our own eyes.

This video was funded by the CaSTL Research Center and comes with a video game called Bond Breaker. Aside from being almost addictive to play, it’s extremely useful. Playing will give you an intuitive understanding of how atoms (and their subatomic particles) interact to form chemical bonds:

Bond Breaker Educational Game

Explore Further

Stated Clearly animations about atoms and molecules:

PDF of John Dalton’s Original book on atomic theory:

A much more readable overview of Dalton’s book:

Scientific Paper by CaSTL researchers on how to “shrink” light for use in atomic resolution imaging:

For Teachers

The content of this video meets criteria in the following Disciplinary Core Ideas defined by Next Generation Science Standards. Use our videos to supplement classroom curriculum.


Our videos benefit from guidance and advice provided by experts in science and education. This animation is the result of collaboration between the following scientists, educators, and our team of creatives.

  • Ara Apkarian, PhD
  • Danielle Watt, PhD
  • David O. Conover, PhD
  • Eric Potma, PhD
  • Eric T. Parker, PhD
  • Johana Revel, PhD
  • Joonhee Lee, PhD
  • Suhail Alhejji
  • Tom Cochran
  • Venkat Bommisetty, PhD
  • Wilson Ho, PhD
  • Jon Perry
  • Anthony Danzl
  • Jordan Collver
  • Tyler Proctor


In this video we state that Jabir ibn Hayyan was Arabian, but there is uncertainty about this among historians. He may have been Persian. Like many influential people of his time, his story is almost mythical, with multiple origins being found in historical writings.

Also, he never used a Bunsen burner (which is what we erroneously drew him using) that wasn’t invented until 1856. Jabir likely burnt wood or other solid fuels to heat his reactions.