I've read the article about personal engagement in Facebook, after user failed to buy or visited with NO ACTION my website. Please give me idea if it possible or not. I install the pixel. I have for example different groups of users. 1) who bought something 2) who was with no action 3) who signed for free trial but didn't care about etc. Can I show personal ads to that users? I mean what is minimum group size to show them remarketing in Facebook? Can it be for 1 user only or it should be minimum ten for example?