The process of decision making taking place in the brain is much more complex than it might seem at first glance, even when the process in question is a simple choice, like the choice beetween an apple and an orange. Neuroeconomics focuses on exploring those inner processes. It studies both simple and much more complex choices such as intertemporal choices, decision making in social situations and decision making under conditions of risk and uncertainty. By studying the central organ of decision making, the brain, with devices like EEG, MEG, fMRI and others, this scientific discipline arrives at insights that help explain and reveal what influences the decision making process. Neuroeconomics is a relatively new interdisciplinary scientific branch that blends knowledge from economics, psychology and neuroscience. In combining formal models of decision making from economics with data describing psychological processes that take place during decision making, it makes up a complex system enriched with insights and methods that come from neuroscience. These are the foundations of this new science, neuroeconomics, which by combining all the aforementioned approaches tries to explain the biological foundations on which the economic decision making process in human beings is founded.