For those who are just first learning about click chemistry, it makes attaching two larger molecules together very, very simple. It can be done under very gentle conditions (like in water), and has exceptional selectivity. Like it's so selective you really don't need to worry about other things happening on the timescales these reactions occur and can be cleaned up (an hour). There are two types of click chemistry, one that uses copper as a catalyst and one that doesn't. They both opened the world of chemically "stapling" two things together to literally all bench scientists. I cannot overstate how transformative this has been to biological science.