The first single off of Californication describes the struggles addicts go through to get sober and how they are viewed different when they return to reality. Scar tissue is a good comparison, as it is a sign that there was damage but it healed, and it could also refer to the healed areas where an addict used to inject themself.

This song won them a Grammy in 2000 for Best Rock Song, and peaked at #8 on the Billboard Charts.