Nicolaus Copernicus is not famous for his contributions to reproductive science, but rather for his contributions to ASTRONOMY. (Although he did work as a physician for a time, studying medicine, as well as many other things such as economics, classical history, linguistics, and politics.)
His famous theory was that it was the sun at the center of the universe, rather than the earth. Although there were limitations to the Copernican model, it was an absolute breakthrough idea. One such limitation was the fact that he still used a universe-based model, rather than a solar system based one. In fact, our sun is at the center of our solar system, and definitely not the universe, or even the galaxy.
His theory was heliocentric (sun-centered) rather than geocentric (earth-centered). The geocentric model is also called the Ptolemaic model, after the Greek philosopher Ptolemy. Decades after he first came up with the heliocentric theory, Copernicus published his ideas in De revolutionibus orbium coelestium (In English: On the Revolutions of the Celestial Spheres). It summarized the theory. Besides the idea that everything orbited the sun rather than the earth, the significant parts included the idea that retrograde and direct motion could be explained by the rotation of the earth, the idea that there is no one center of all the celestial circles and spheres, and the idea that the earth has more than one motion (orbiting the sun, as well as rotating around). Most of these ended up being true, as they were later proven by other great scientists.
Copernicus's heliocentric theory began what became known as the Copernican Revolution, sparking the ideas and experiments of later scientists like Tycho Brahe and Johannes Kepler. Most significantly, Kepler modified Copernicus's theory from perfect circles to ellipses, and thus solved many issues with the original model--especially the ones having to do with retrograde motion.