What is an important theme of the story?

There are several important themes in the novel Little Women.  One important theme that is prominent throughout the story is that of womanhood and femininity.  Societal ideas about womanhood and femininity are contrasted with less traditional ones.
An example of this theme is the contrast between Meg and Jo.  Meg is more traditionally feminine than Jo.  She often reminds Jo to be ladylike, as do the other sisters.  Meg has "a sweet mouth, and white hands" (Chapter 1).  White hands indicate that she is careful not to let her skin tan or freckle, and also that she tries not to do too much manual work.  In the mid 1800s, fair skin with no freckles was desired among many young ladies.  Jo, on the other hand, is "thin, and brown, and remind[s] one of a colt."  This comparison of Jo to a colt shows that she is considered wild.
Meg scolds Jo for being too masculine.  She tells her sister that she is "old enough to leave off boyish tricks, and to behave better."  Jo dismisses this, stating that she wishes she had been born a boy.  She does not like the societal expectations placed on young ladies.
Meg's traditional femininity conflicts with Jo's independent, more masculine spirit and attitude.  Throughout the story, this theme is further shown.  Meg marries and has children, while Jo moves to the city to live independently and start a career.