Kin selection theory has enjoyed much success with its original problems like the evolution of the eusocial insects, but it has also predicted many new phenomena. I highlight three recent examples from our lab (1) The slime mold Dictyostelium discoideum cooperates with kin but also recognizes non-kin and expresses conflict genes that evolve rapidly. (2) In the seeds of flowering plants, conflict between the mother, endosperm, and embryo generates evolutionary arms races. (3) Honeybee workers are pushed by their paternally imprinted genes to lay eggs. In the last part of the talk I argue that similarly fruitful theory may be available for interactions between species, because they can be understood in terms closely parallel to Hamilton’s kin selection rule.