What asset makes the most millionaires?

I'm genuinely curious about what asset has been the most successful at creating millionaires. Could you please elaborate on this? I've heard rumors about certain cryptocurrencies and stocks that have made some individuals extremely wealthy, but I'm not entirely sure which ones are the most notable. Is there a particular asset class or investment strategy that stands out in this regard? I'd love to hear your thoughts on this matter, as I'm always interested in exploring new ways to grow my wealth.