Anything that involves our activities in space - look at the Voyager probes and New Horizons. Getting those things to send signals across the solar system, predicting their trajectories with enough accuracy to use other planets to slingshot them places: it seems impossible but we've done it and continue to advance. Those pictures of Pluto were sent by a weak electromagnetic wave across billions of kilometres of space. Just thinking about it makes the hair on the back of my neck stand up.