In philosophy, the study of the relationship between parts and wholes is known as mereology, and chemical interactions present fascinating ways of testing some such theories. In chemistry, it turns out, wholes are much more than the mere sum of their parts. Take a bunch of carbon, for instance, and depending on how its molecules are configured, you could end up having two fundamentally different substances, even though they are made of exactly the same single ingredient.
You could end up with a diamond, which is clear and hard as hell, but is a crappy electrical conductor... or you could end up with graphite, which is opaque and weak as shit, but has great conductivity. Of course, if you subject a diamond to sufficient heat, as Antoine Lavoissier did in 1772, you would be able to scientifically prove that (despite the mind-numbing marketing campaign with which so many women have been brainwashed in America) diamonds are NOT forever :)
But I digress... As Professor Al-Khalili explains, even though the world around us is made up of roughly 92 elements, it's the various ways in which they can combine and interact with each other that explains the various objects and substances we see everywhere.
Configuration is key, and it opens up an astonishing chapter in the history of chemistry, a window into the realization of an ancient alchemical dream: the ability to turn one basic element into another. The discovery of nuclear fusion would also help us understand how the sun fuels itself, and in its most dramatic and practical application, it would give rise to the atomic age.
Learn more about the incredible work of Lisa Meitner here and here.