Recent discussions have focused on the potential IPOs of major companies like SpaceX, Anthropic, and OpenAI, and their significant valuations. This has also ignited a debate about index inclusion criteria, specifically for these large, potentially trillion-dollar companies joining indexes such as the S&P 500. Opponents of inclusion often cite hidden agendas or misguided investment views. Some active investors see inclusion as a threat to passive investing, while academics and experts warn of risks for retail investors and retirees due to the companies' current unprofitability. Politicians express concern about rewarding billionaires through government pension funds. The article aims to clarify index construction, their market roles, and the impact of including these new tech giants on the active versus passive investing discussion. Indices are defined by their constituents, determined by factors like market capitalization, listing age, liquidity, and profitability. Companies are weighted within an index through equal weighting, price weighting, or market capitalization weighting, with the latter being the most common. Index levels are calculated by converting constituent market prices into a single value, and these levels are updated to reflect market changes. Inclusion and exclusion of companies from an index can occur due to acquisitions, bankruptcies, new listings, or shifts in market capitalization, requiring adjustments to index mechanics. Ultimately, while the index level may remain unchanged during a company's addition, its fundamental characteristics, such as risk and earnings potential, will be altered going forward.