Do you have a coworker that you want to make friends with, but you haven't been having much luck? Maybe the person is particularly difficult, or maybe, for whatever reason, the two of you just don't click. If getting close to this person is important to you, there are a few more things you can try before you label the person impossible.
One thing you can try is inviting the person out after work or on a weekend. Even if the person refuses, the fact that you offered to see them outside of the times you normally do will make them feel good about themselves. If they decline and say that they have other plans, wait about a week, then ask one more time. If they still say no, don't ask again- doing so will seem pushy.
A quick note here about that advice- if you and the person you are inviting out are of opposite genders, make sure that it's obvious that you aren't asking them out on a date. Offer to let their significant other come too if they have one. If not, consider asking out a large group of your coworkers.
Another thing you can do is making sure to say the person's name frequently. It sounds really easy, but studies have shown that saying a person's name makes them feel positive towards you. Just make sure you don't use their name in negative ways (such as when expressing condolences).
If you find yourself with some extra time at work, try going to the person and offering to help them. Even if all you do is something as simple as picking something up from the printer for them, it will be remembered. Sometimes all it takes is getting yourself on somebody's mind to get them to warm up to you.
These are the best things you can do to make friends with the people you work with. if you still don't understand the importance behind getting close to your coworkers, look at this article on how helpful it can be for your career and your future. And good luck!