Even relatively simple instruments available to retail traders go ridiculously deep. A good example are the VIX ETFs like VXX.
Level 1: Stocks
Level 2: Stocks are aggregated into the S&P500 index
Level 3: There are options on the index
Level 4: From volatility implied by the options, the VIX index is calculated
Level 5: Futures on the VIX
Level 6: The ETF holds futures on the VIX
And arguably level 7 is that the ETF uses a predetermined strategy to trade the VIX contracts, which is what ultimately determines the returns.