How do teens express their individuality

What are the ways of expressing the individuality?
Why do young people join the group?
What groups are there in the world?

Teenagers have a particular relationship with the world. They always try to express their individuality.
To express it they try to
show off;
show a rebellion against the parents, the regime, society;
reject everything;
join the group or the organization.

One of the most popular way of expressing the individuality is to join the group or the organization. Teenagers join the group because
they want:
To achieve something
To change the world for the best
To try out all sorts of options
To be in a collective
What other reasons can you suggest?

There are different groups and organization in the world. They are:
Bikers;
Hippies;
Environmentalists;
Hackers;
Punks;
Ravers;
Scouts;
Volunteers.
What other groups do you know?