Heart radical at the bottom - 您 is 'you, with my heart underneath' - addressing someone with sincerity and respect. A late-coined character (Yuan/Ming era) specifically to convey this nuance; the heart isn't decorative but the very source of the politeness.
你 sits on top - both supplies the sound (你 nǐ → 您 nín) and provides the 'you' semantics. 您 is a polite/formal upgrade of 你: the same word, lifted onto a heart, expressing respect. Used for elders, teachers, customers, strangers.
