Ninety-five percent of the present mass-energy density of the Universe is dark. Twenty-five percent is in the form of dark matter holding together galaxies and other large scale structures, and 70% is in the form of dark energy driving an accelerated expansion of the universe. Dark matter and dark energy cannot be explained within the standard model of particle physics. In the first lecture I will review the evidence for dark matter and the observations that point to an explanation in the form of cold dark matter. I will then describe the expected properties of a hypothetical Weakly-Interacting Massive Particle, or WIMP, and review experimental and observational approaches to test the hypothesis. Finally, I will discuss how the LHC might shed light on the problem. In the second lecture I will review the theoretical foundations and observational evidence that the dominant component of the present mass density of the Universe has a negative pressure, which leads to an accelerated expansion of the Universe. I will then describe various approaches to understand the phenomenon. Finally, I will describe an observational program to understand the nature of dark energy. The third lecture will describe the issues and models associated with primordial inflation, the purported rapid expansion of the universe in the first fraction of a second after the bang. Models of inflation also involve beyond the standard model physics. The lecture will describe how present observations can shed light on events that occurred in the first second of the life of the universe.
