The current understanding of the constituents of our universe is rather complete but also bizarre. While we can describe the current cosmological observations with a model with only six free parameters, most of the energy density in the universe is in a form that has not been yet detected. Specially bizarre is the discovery that the universe is currently accelerating (the so-called dark energy component), thus going through a "micro-inflation" phase. In the last couple of years there has been significant progress in understanding what maybe be the cause of the accelerating engine in the universe. In this talk I will review the current status of our understanding of the dark energy problem, providing a review of our current findings and will present new results from the Atacama Cosmology Telescope that shed light on the nature of dark energy.