Market capitalization, or market cap, is the total value of a company's outstanding shares of stock. Tesla, an electric vehicle and clean energy company, had maintained a market cap above $1 trillion since November. Recent data reveals a significant drop in European sales. - Tesla's stock price decreased by 8% on Tuesday, leading to a market capitalization below $1 trillion. - January sales for Tesla in Europe fell by 45%, contrasting with a 37% increase in overall electric vehicle sales in the region. - The decline in Tesla's stock significantly impacted the performance of mega-cap technology stocks. - Elon Musk's net worth decreased by $15 billion due to the drop in Tesla's stock price.