When at the grocery store you should never look into the beams of light in the scanner at the checkout line why not?

You should never look into the beams of light in the scanner at the checkout line because they emit laser light, which can potentially cause harm to your eyes. Direct exposure to laser beams, especially those used in barcode scanners, can lead to temporary or even permanent vision damage. It's best to keep your eyes away from the scanner to ensure your safety.