This is an interesting profile of Terence Tao as an ~8 year old: https://gwern.net/doc/iq/high/smpy/1984-clements.pdf, written by somebody who seems to have been well-versed in working with mathematically precocious children. It's interesting less for how good at math Tao already is but a peek into how he went about learning and doing math at a time when the subject matter was still accessible to, say, most users here. Among other things, what might be called his "openness to math experience" and independence are both remarkable.