How to completely delete data from Samsung phone?

So I was wondering, how do you go about erasing photos ,messages and other data on Samsung galaxy phone? I have tried factory reset my phone, but some guys said that data still remain on the device and can be easily scanned and recovered.

So, what other methods exist for 100% erasing data on Samsung galaxy phone without recovery?

Thanks in advance for any help.

from Android Authority Forums http://ift.tt/2nv6VnT
via IFTTT