"Tattoos on the Heart" is a book by Gregory Boyle, a Jesuit priest and founder of Homeboy Industries, an organization that helps former gang members reintegrate into society. The book shares stories from Boyle's experiences working with at-risk youth in Los Angeles, highlighting themes of compassion, redemption, and the power of community. Through personal anecdotes and reflections, Boyle emphasizes the importance of love and understanding in overcoming adversity. The title refers to the lasting impact of these experiences, suggesting that the lessons learned and connections made are indelible, much like a tattoo on the heart.