How do I get rid of small tiny black bugs flying around the house?

Usually whenever the door is opened or the patio door is opened with the screen closed, these small tiny black bugs keep coming inside. They are sometimes as small as an ant or sometimes even smaller than an ant. They're really annoying and they keep flying around. It's so hard to kill them because they won't even land on a surface. Today I was finally able to kill 3 of them in my bathroom. I don't know what they're called, but does anyone have any idea what they might be called and how to get rid of it? I'm afraid they've laid eggs somewhere because they keep multiplying. It's so hard to find them to kill.