This tiny stingray is a robot powered by rat muscle cells. After going to the aquarium, lead scientist Kit Parker told his teammate "we're going to build a ray, we're going to build it out of a rat, and we're going to make it light-guided." This project was mainly done for the wow factor, but Parker hopes to one day build a whole human heart out of genetically engineered tissue using this type of technology.

Researchers in Norway built a Pac-Man maze one millimeter across, introduced some microorganisms and their predators into them, and let the game begin. The team wanted to build a more realistic environment in which to observe the organisms interacting with each other and with the world.

Marvel Comics introduced Iron Man Tony Stark's successor, Riri Williams. The character is a black woman who overcame inner city violence to enroll at MIT at 15 years old. Some comic book fans wish Marvel would hire more women and people of color: Riri Williams was created by Brian Michael Bendis, a white man. But Bendis feels the character is a step in the right direction if it helps excluded groups feel included in comic books.

When Juno arrived at Jupiter this week, it carried an adorable crew of three LEGO figures, representing the Roman god Jupiter, his wife Juno, and Galileo Galilei. The figures are meant to get children excited about science and technology.

This exoplanet is called HD 131399Ab. It's part of a triple star system, sits further away from its parent star as Pluto, and is four times larger than Jupiter. Scientists are wondering how it got so far away from its host star without being flung into space by the other two stars.

YouTuber Grant Thompson filled a six-foot balloon with liquid nitrogen and caught the whole thing on video.

NASA's Kepler Spacecraft's Twitter fell victim to a Twitter hack. A photo of an underwear-clad butt was tweeted at Kepler's almost 600,000 followers and briefly appeared on the NASA homepage. Lots of people found it the perfect opportunity to make space-butt jokes.

The Chinese Academy of Science finished up its 500-meter radio telescope. It will be open for use in two to three years, and may be used to continue studying gravitational waves... and maybe even find extraterrestrial life. 9,000 people were displaced to build the telescope.