(be or become aware of)
se rendre compte de
→ She realized the significance of what he was trying to do.
to realize how ..., Do you realize how long it takes? Est-ce que tu te rends compte du temps que cela prend?
→ People don't realize how serious this recession is
to realize (that) ... se rendre compte que ...
→ I realize that this is your first job.
→ Finally I realized that she would not be coming back.
We realized that something was wrong. Nous nous sommes rendu compte que quelque chose n'allait pas.