A polynomial is called an identity if it is identically zero. To test whether a polynomial (given in some nontrivial way) is an identity is called Identity Testing. It is a central open problem in complexity and lower bounds area. In this talk we will consider a special and well studied class of identities - those that are sums-of-products of linear forms. We will almost completely explain the structure of such identities by using a notion from incidence geometry - Sylvester-Gallai Configurations. Qualitatively, we show that identities are just Sylvester-Gallai configurations. Quantitatively, we get that simple and minimal depth-3 identities of top fanin k and degree d have rank at most O(k^2) over reals and O(k^2.log d) over any field. This gives, using standard results, a deterministic black-box identity test for depth-3 circuits that has significantly smaller time complexity compared to the previous results.