crys·tal·lin 
(krĭstə-lĭn)
(krĭstə-lĭn)n.
Any of several proteins found in the lens of the eye in vertebrates and certain invertebrates.
[Latin crystallum, crystal; see CRYSTAL + -IN.]
- keep head
- keep/hold (one's) peace
- keeping
- keep/know (one's) place
- keep kosher
- keep nose clean
- keep nose to the grindstone
- keep off
- keep (one's) chin up
- keep one's chin up
- keep one's end up
- keep one's eyes open
- keep (one's) eyes open/peeled
- keep one's eyes peeled
- keep one's fingers crossed
- keep (one's) head
- keep one's head
- keep (one's) nose clean
- keep one's nose clean
- keep one's nose to the grindstone
- keep one's peace
- keep one's place
- keep (one's) powder dry
- keep one's powder dry
- keep (one's) shirt on