Baby Yoda's in danger, folks. The Mandalorian revealed that his pursuers are trying to capture him to "extract" something from him, and we think we know what they're after: midi-chlorians. If you're scratching your head trying to remember what midi-chlorians are, we've got a quick recap of what we know so far.
Midi-chlorians are, essentially, the science/magic behind the Force. They're first explained in The Phantom Menace, when Qui-Gon Jinn explains the workings of the universe to young Anakin Skywalker. "Without the midi-chlorians, life could not exist, and we would have no knowledge of the Force. They continually speak to us, telling us the will of the Force. When you learn to quiet your mind, you'll hear them speaking to you," he says.
As described in the movie and other bonus materials, midi-chlorians are microscopic, intelligent organisms that exist in all living beings in the Star Wars universe. The higher an individual's "midi-chlorian count," the higher one's sensitivity to the Force, which in turn means a higher possibility of strong Force abilities. This concept is at the root of Anakin Skywalker's unique status and incredibly strong powers: when he's first discovered in The Phantom Menace, he has the highest count ever recorded, at over 20,000 per cell.
Although midi-chlorians occur naturally in all life in this universe, the prequel trilogy notes that there are some ways of manipulating the midi-chlorians to achieve the will of others or simply the will of the Force. It's suggested that Anakin's birth is, technically, the result of one such event: he has no biological father, only a mother, and the idea is that he was conceived by the midi-chlorians at the will of the Force, which is why he has such a high midi-chlorian count and such a strong connection with the Force.
Force-sensitive beings have especially high midi-chlorian counts, and some dark medical technology could be developed from that knowledge — which might explain why they're after Baby Yoda. Wookieepedia explains that a blood infusion from a being with a high midi-chlorian count could save a being who would otherwise die. While it wouldn't result in a transfer of Force sensitivity, it would bring someone back even from what should have been a fatal injury. Technology around midi-chlorians is constantly changing in the Star Wars universe, so there could be several reasons why Baby Yoda's pursuers want to capture him and extract midi-chlorians — but in all likelihood, all of those reasons could put him in serious danger.