I've discussed ketchup rheology a couple of times in the past (1, 2), but a new TedEd video really does a great job of visually showing the rheology and also getting into some of the details.
Early in the project I had a few emails back and forth with George Zaidan, one of the creators. He's has a great talent for writing scripts, so much so that I have forever sworn off even attempting to ever write one. You can read his writing and easily imagine the finished product - that's quite a skill. I've read screenplays out of Hollywood [*] that aren't anywhere near the quality.
Check out the video when you have 4:29 to spare.
[*] I have this friend who knows this guy who acted with...who got me the script for this movie. I had my people call his people so we could do lunch, but we never could DeNiro to show up and so the whole project fell through. (The first sentence is entirely true. The verity of the second one is left as an exercise to the reader.)