xkcd has an eye-opening graphic this week showing how many planets have been discovered. If you click on the image, it will open a full-size version of the cartoon.
It was not so long ago that exoplanets (planets outside our own solar system) were hypothetical. That is, astronomers assumed other star systems could include planets, but there was no observational evidence. Technology has progressed to the point now that finding extrasolar planets is a walk in the park. Finding Earth-sized planets is more of a challenge, but at least we know they likely exist.
Getting there, however … not so easy.