Where do you live?

It looks like a "paper wasp" nest, could be one of many species.

How did it get between the screen and the window?

There's the wasp photobombing the third photo.

In general, you'd wait until night when they're less active, and squirt them with a good long-range insecticide--they make wasp sprays especially for that. Have a clear escape route. You want to get this taken care of before it gets bigger...

I'm pretty tolerant of wasp nests, but that one is WAY TOO CLOSE.

Thank you guys for your response

I live in Dallas, Texas. The screen had a dent that caused a small opening.

So it's a wasp nest. I will get it taken care of. Thank you again.

Paper wasps, as a rule, are fairly gentle. I have removed the nests they make many times with no problems. Those paper wasps are beneficial insects because their primary food source is insects we consider pests.

However, in the location shown the nest must be removed, preferably at night when the wasps are in the nest resting. A cheap hair spray may well work as well as a more expensive wasp poison. If a wasp poison is to be used be sure it is one that will kill wasps.