Well, if you guessed three, then common knowledge says you are at least partly right, but then maybe not. Include time, also referred to as time-space, and you have at least what is thought of as the four known dimensions. Modern physicists theorize the probability of perhaps seven more dimensions in the physical universe, yet unseen. Dimensions undetected by our senses, bathed in the forces of gravity and holding together the fabric of the universe.
String theory, one of the more popular theories held by some modern physicists, suggests that the smallest particles of the universe consist not of particles but instead looped strings that vibrate at frequencies beyond our observation. Too small to be detected or observed, scientists will have the ability to test some of these theories in the particle lab this weekend when they do a bit of particle smashing. Not since Einstein's theory of General Relativity have the ideas of the make up of the universe been close to being overhauled.
Physics is like philosophy or better yet magic. It delves into a realm of ideas and scientific theory which tests the nature of reality. What we observe, how it is observed and how mass energy operates in the universe is stunning in its complexity and utter bizareness. Now, most of this falls well beyond my limit of understanding, yet even are most brilliant scientific minds can't explain how the world operates, let alone explain what may be going on in those other seven dimensions.
I'm thinking at least one big party.