You never know what you’ll find when you pop the cover of an iPhone or Samsung Galaxy, but you know it won’t be pretty. The repair shops we contacted report a wide range of effluvia inside, including metal shavings, construction dust, tobacco leaves, and “what can only be described as green slime,” says Oz Rahman, VP of quality assurance at Batteries Plus Bulbs.

Fixing phones is clearly not a job for the faint of stomach.

“The most horrifically common and disgusting thing our repair team deals with are finger oils and food caking in around the home button,” says AJ Forsythe, CEO of iCracked, an onsite repair and buyback service. “It is absolutely the grossest thing to clean as these things do not tend to fall out — ever — thanks to Apple’s very secure design.”