When an archaeologist finds a jar or an amphora, can they tell what food it contained and how?

Dr. dig responds:
Sometimes archaeologists are able to tell what kind of food a jar or an amphora once held because there are actual remains of the food still left on the inside. The food remains won't still be fresh, of course, but the decayed remains can be studied under the microscope. Remains of seeds, plant fibers and pollen help archaeologist identify the food the jar once held.

Archaeologists also know that particular jars or amphoras of a certain shape contained certain foods. Just the way you are likely to able to recognize a ketchup bottle from a soda bottle, an archaeologist can tell the difference between one kind of amphora that contained wine and another that held olives.

Here's a good game to play at home or at school: Draw just the shapes of different food containers but do not label them. Imagine that you are all archaeologists and you must try to determine what food these shapes contained. Some shapes may be immediately recognizeable; others may be harder to figure out. Why are some shapes more suitable for one kind of food but not another?