The 4 and 5 digit codes on fruits and vegetables in stores are called "PLU codes" (Price Look-up codes) and they primarily serve to identify the specific type of produce, its size, and most importantly, whether it was grown conventionally (4-digit code) or organically (5-digit code starting with a '9').

4-digit codes: These are for conventionally grown produce with chemicals (4011 for a regular banana, 4012 for a conventional carrot).

5-digit codes starting with "9": These represent organic produce (94011 for an organic banana, 94012 for an organic carrot).

5-digit codes starting with "8": These are for genetically modified (GMO) produce. An example could be 84011 for a GMO banana.

Remember, conventionally grown produce uses 4 digits, organic uses 5 digits starting with "9" and GMO produce is typically marked with a 5-digit code starting with "8."

Remember to wash your hands when handling these types of fruits & vegetables so it will not absorb into your skin.