Recycling can be confusing enough as it is. To help, here's what those little numbers in recycling symbols actually mean.

They're called Resin Identification Codes. Follow BI Video: On Twitter More from Science Ever wonder what those small numbers on the bottom of your plastic bottles and takeout containers mean?

ASTM committee on additive manufacturing technologies is developing a standard-guide for mechanical testing of plastics used in AM. Additional changes could be coming for the Resin Identification ...