Abstract: A system comprising a shopping cart and a multiplicity of modular and reusable containers, where the containers can be placed upon the shopping cart and removed from the shopping cart by a customer, according to the customer's needs. The containers have an encircling wall and a floor connected thereto, where the wall has protruding and sunken parts forming a shape that enables compactly stacking the containers, where each two adjacent containers are engaged in an interlocking manner.