Meaningful educational activities and cognitive tools might improve students' active involvements in the teaching-learning process and encourage their reflections on the concepts and relations to be investigated. It is claimed that usage of manipulatives not only increase students' conceptual understanding and problem solving skills but also promotes their positive attitudes towards mathematics since they supposedly provide "concrete experiences" that focus attention and increase motivation. A concrete experience in mathematics context is defined not by its physical or real-world characteristics but rather by how meaningful connections it could make with other mathematical ideas and situations. For instance, a student might create the meaning of the concept "four" by building a representation of the number and connecting it with either real or pictured blocks. Computer manipulatives, also called virtual manipulatives, may provide interactive environments where students could pose and solve their own problems to form connections between mathematical concepts and operations, and get immediate feedback about their actions. Hence, it is necessary to design specific math manipulatives focusing at different mathematical concepts. Virtual manipulatives might also provide further advantages over physical manipulatives by eliminating some of the constraints they impose on the task. In this paper, virtual manipulatives in mathematics education will be introduced, their main characteristics will be explained and the implications of the usage of virtual manipulatives in mathematics classrooms will be thoroughly discussed.