Mechanical twinning occurs in metals having which type(s) of crystal structure(s)?

Mechanical twinning occurs in metals having body center cubic and hexagonal closed packed structures. Twinning is said to occur when a portion of a crystal takes up an orientation that is related to the orientation of the untwinned lattice in a definite symmetrical manner. 

During photosynthesis, plants transform electromagnet energy from the sun into chemical energy.