Billionaire Ken Griffin, founder of Citadel, has been aggressively buying two ETFs recently. Griffin, known for his successful investment strategies, has been accumulating shares of these ETFs at a rapid pace. The first ETF that Griffin has been investing in heavily is the SPDR S&P 500 ETF Trust (SPY), which tracks the performance of the S&P 500 index. The second ETF that Griffin has been buying hand over fist is the Invesco QQQ Trust (QQQ), which tracks the performance of the Nasdaq-100 index. Griffin’s interest in these ETFs suggests that he sees potential for growth in the stock market and is positioning his portfolio accordingly. Investors may want to keep an eye on these two ETFs as Griffin’s moves could indicate opportunities for growth in the market.