? Safe Microwave Plastics?

Thinking we "need" some microwave-safe plastic cookware like omelet makers. How can we tell, before using, if the plastic is really microwave-safe?

Concern: Virtually all our plastic storage containers have been used to microwave stuff and they all have pits & roughness on the inner surfaces as an after-effect. I assume it's from the heat of the contents, not the microwaving itself. Regardless, it looks ugly and we're concerned that chemicals in the plastic could be leeching into the food.