Congratulations! You have correctly identified the "secret ingredient" in agarose. This is a picture of seaweed. Agarose is a chain of sugar molecules, and is extracted from seaweed.
Manufacturers prepare special grades of agarose for scientific experimentation. Because the agarose undergoes much commercial processing it is very expensive.
The photograph of the seaweed was used from Biology, 3rd. Edition, by Campbell.
To the left is the more familiar state of seaweed, as far as molecular biologists are concerned. As mentioned before, high grade agarose is expensive. Guess how much this 500 gram bottle costs. Would you believe $200?!?
Now it's time to learn what we do with this powder to separate DNA molecules, so let's return to the previous page.