Is there anything but yeast in a packet of baker's yeast?
Since you mention grains, I assume you're talking about active dry or instant yeast. The short answer is that either way, you're seeing granules of yeast plus dead yeast cells and dried growth medium, with the ratio of each depending on the type.

The Wikipedia page on Baker's yeast has plenty of detail about the various types of yeast. Notably, it lists several stages of processing:


cream yeast - basically just yeast siphoned off, in liquid form. It's perishable enough that you can't generally buy it.
compressed yeast - essentially cream yeast with most of the liquid removed, most commonly sold in the form of cake yeast. It's still perishable, but lasts long enough to sell.
active dry yeast - fully dried, "coarse oblong granules of yeast, with live yeast cells encapsulated in a thick jacket of dry, dead cells with some growth medium".
instant yeast - similar to active dry, but smaller granules and more live yeast per volume. This makes it more perishable but easier to use. (On Food and Cooking mentions that it's "in the form of small porous rods that take up water more rapidly than granules.")