Big Data makes the difference in many different sectors, increasing companies’ competitiveness or improving their decisions making process. Insurance companies, banks (when granting loans) or human resources departments are example of daily usage of algorithms in pursuit of efficiency. However, for Cathy O’Neil, Ph.D. in math from Harvard and postdoc at the MIT math department, the design of these formulas brings important questions to the table: Allow algorithms equal opportunities? Make sense under a democratic system? Perpetuate inequalities? Big Data evaluates risks, checks our health, assigns profiles and highlights one candidate over others, but why are they not transparent? Are they under some kind of regulation? Welcome to the darkest side of Big Data.