A HomeMade Experiment: What did I make?

So, please don't get grossed out. Just read and decide.

When we came home from Camp, we had around 1/2 gallon of milk in a gallon container with the expiration date of 3 days later waiting for us. But it was severly curdled. Or at least looked bad-seperated. So I dumped it.

A few days ago, I poured the girls milk in their sippy cups for breakfast. A few hours later they were wanting more, so I said bring me your cups and I will get you new ones with juice. When I dumped these cups in the sink, they were seperated too-- not chunky, but not smooth. Of course, I was *slightly* concerned!

I poured some in my coffee, and it seperated immediately. Sooo weird. Like making buttermilk.

I ended up putting some in a measuring cup so I could watch it, and I threw the rest away. Over the next 30+ hours, the milk sat in the cup on the counter uncovered. The next day, I dumped it in the sink to wash the measuring cup, and here is what happened: (if I am correct, this is up to you to decide)

The "whey" poured from the top first, a watery-milky substance. Then the second half plopped out like yogurt from a cup. The crazy part is this: It never smelled bad.

So, what did I make? :-) This is a real question, as I don't know. I am just combining the meager knowledge I have from reading about making yogurt and sour cream and kefir... none of which I actually know how to do. I have just read some out and about in the blogosphere. Hmmmm.