The US stock market is experiencing a significant surge in penny stock trading, prompting warnings of frothy markets. Many of these penny stocks, defined as shares trading below $1, are seeing volumes surpassing those of major companies like Tesla and Apple. This trend is largely driven by retail investors targeting cheap but volatile names in hopes of quick profits. Seven of the top 10 most traded US equities are penny stocks. None of the companies involved in this surge are currently profitable, raising concerns about the sustainability of this trading boom. Additionally, meme stocks are back, and the stock market is near records.