On the left, the first batch of Marshmallows. Short, slumpy, and not so much bubblage in the internal structure. Because of their density, they end up sticking around on your tongue for a lot longer, and ending up being a little sickly sweet.
On the right, the second batch of Marshmallows, using a proper candy thermometer. Tall, bubbly, nicely square. These melt way more readily, so you don't end up with vanilla sugar-slime in your mouth.
Case in point: The marshmallows on the left got put back in their bag to be made into rice krispie squares or some such thing.
The Marshmallows on the right?
I ate them!