Social Penetration Theory proposes that relationships develop through reciprocal self-disclosure from superficial to intimate topics over time. It is likened to an onion with layers being peeled back through breath and depth of disclosure. Relationships progress through 5 stages from orientation to stable partnership or depenetration. People regulate intimacy based on weighing rewards against costs using standards of comparison to their current relationship and alternatives. While influential, the theory is limited in scope and not fully data-backed, and disclosure's impact can vary between increasing and decreasing closeness.