What kinds of things have you researched in the name of writing?

Sometimes it’s harmless stuff: what plants grow in the winter months, when are cucumbers at their best, lunar cycles, google maps locations, hair color diagrams, eye color diagrams, synonyms, color wheels, pictures of stone
Sometimes it’s stuff that probably gets me on some strange watch list: tiny weapons that could kill someone, small sharp things, how to naturally decompose a body
Sometimes it’s stuff that will make someone ask questions: signs you’re in an abusive relationship, anger management tips, signs someone is angry