Quantum entanglement
Scientists are trying to use quantum entanglement for many different things. Some things are sending completely secret messages (passing encrypted notes that can't be understood if intercepted), and making super computers faster than ever before thought possible. However, entanglement between a pair of particles is a very delicate thing and is easily destroyed. Because of this, it is difficult to use quantum entanglement to do these things. Currently, many scientists are working on making stronger systems where entanglement is stronger and lasts longer to try to do these things more easily.