Oil production rate, as well as the production rates of other natural resources, is constrained by limits imposed by Geology, by Thermodynamics and even by Economy. Such constrains on oil production rate may have severe effects on our economical and societal system. Peak Oil (i.e., the maximum oil production rate, after which production will dwindle) seems to be very close, as oil production is in a plateau for almost six years now. Some public bodies such as the International Energy Agency warn that the observed constraints on oil production are one of the key factors on the onset of the present economic crisis. In this talk, we will review some basic concepts about Peak Oil and its consequences; we will also analyze the status of the alternatives to oil, and how to face a not-so-distant future threatened by scarcity.