Genesis 4:1

And Adam knew Eve his wife; and she conceived, and bare Cain, and said, I have gotten a man from the LORD.

1. Adam and his wife Eve had a sexual relationship (this is obvious if you accept that we are their posterity).
2. Eve conceived and gave birth to a son, named Cain.
3. Either Eve delivered Cain outside of Adam's presence, in which case she told Adam about it by saying, "I have gotten a man from the LORD," or she said this to someone else (perhaps previous, unnamed children), or she was emphasizing to Adam that children are gifts from God.
4. It's interesting that Eve referred to a newborn male child as a "man". Perhaps, their language was not well-developed yet.
5. This is the first use of the title, "LORD" by itself. In the first three chapters of Genesis it is always used as a part of "LORD God." They each seem to refer to the same being.