It's pretty common knowledge that the honeymoon phase doesn't last forever. At some point, the butterflies disappear, the passion starts to dwindle and cute sweet-nothings sound, well, less cute.

But thanks to the people at SoulPancake, it doesn't have to be this way. In their new video, " The Science of Love," they took eight couples who had been together well past the honeymoon phase and showed them how to keep the spark alive.

Watch the video above -- posted on SoulPancake's YouTube page -- to find out how you and your S.O. can keep up the excitement in your relationship for years to come.