Einstein's theory of relativity has been successful in explaining and predicting many gravitational phenomena. Experimentally, however, we do not know how gravity behaves at distances shorter than about 0.01 mm. For example there may be hidden dimensions at short distances. In fact, many theories, including superstring theories and M-theory, require the existence of such extra dimensions. Gravity at very long distances, e.g. billions of light-years, may also be as weird as at short distances. Precision observational data revealed that the expansion of our universe is accelerating. If Einstein's theory is correct, this requires that more than 70 percent of our universe is filled with invisible, negative pressure, energy. This energy is named dark energy, but we do not know what it really is. We thus wonder if we can change Einstein's theory at long distances to address the mystery of dark energy. These considerations let us believe that gravity is the key to tackle the mysteries in modern cosmology such as dark energy, dark matter, inflation and big-bang singularity. Toward this ambitious goal, in this mini-workshop we get together and explore various aspects of gravity and cosmology.