Expressions used in Everyday Spoken English in Social and Professional contexts
To have something 'in the palm of your hand' means to have influence or control over it. If you have an audience 'in the palm of your hand' you have a captive audience who are relating to what you are saying and hanging on every word. Someone who has the power to make a decision might have someone's fate 'in the palm of their hand'. This is an idiom used in both social and professional contexts.