It has been relatively easy for scientists to parse out the various colors that humans are able to see (and some they're not). While it seems like this shouldn't be a terribly difficult task - it proves markedly more difficult for our other senses. While light can easily be broken up and categorized based off of wavelength, other senses such as taste and smell depend on far more complex and subtle differences.
For years, people have distinguished smells based off of distinctly qualitative characteristics - I personally like to use the four basic smells of "sweet" "musky" "stinky" and "gym socks" - but recent research has brought us much closer to constructing an objective set of criteria that distinguish one smell from another.
Noam Sobel's lab at the Weizmann Institute of Science in Israel have been trying to figure out what essential trait causes one molecule to smell differently from another, and they may have found it out.
Sobel looked at specific physical characteristics of various molecules, ranking them on such qualities as size and density of atoms. The result was a scale of molecular smells that ranged from "pleasant" to "odious," a feat that hadn't yet been accomplished when attempting to understand smell.
Though this system certainly has a bit to go before we can start to liken it to the electromagnetic spectrum, having a basic understanding of our olfactory system's response to specific molecule types will make it much easier to understand what is going on when our brain attempts to make sense of the myriad smells we are subjected to every second. And while it may not revolutionize our understanding of the brain, it is a great example of how good science can answer simple questions that affect us all.