Conversation so far:
How did Warren Buffett become a billionaire?
Buffett became a billionaire when Berkshire Hathaway began selling class A shares.
When did Warren Buffett become a billionaire?
Buffett became a billionaire on May 29, 1990, with the market closing at $7,175 a share.
How did Warren Buffett feel about personal wealth?
Buffett had long stated his intention to give away his fortune to charity.

Question: What foundations?
Self-contained rewrite: What foundations did Warren Buffett contribute his wealth towards?