what are 2 basic principles supporting science of fingerprints?

Answer 1

In addition to mystic..'s answer, I would like to add that fingerprints become possible because in addition to water, our sweat also contains some oils which don't evaporate and thus enable the fingerprints to be lifted by the experts. If that were not the case, we ca't get a fingerprint! Gloved hands for example don't leave fingerprints.

Answer 2

1-each persons' prints are unique
2-your prints don't change