The major problem of the study of the mean curvature flow is to understand the singularities. There are several models of the singularities, and the most important model is the self-shrinkers. The self-shrinkers are homothetic shrinking solutions of mean curvature flow. They are also the minimal submanifolds of the Gaussian space, so one of the approaches to study self-shrinker is using the techniques in minimal surface theory. In this talk, I will discuss some recent progress on the research of self-shrinkers. In particular, I will discuss the structure theory of self-shrinkers in R^3.