There are two types of things you see in a lens: large things and small things. The largeness is made by the convex lens' thickness making things look larger or closer than they really are. The smallness is made by concave lens that are thinner, making it appear really small. Concave lens look a little bit like this: )( and a convex lens looks a little bit like this: (). A concave lens is curved like this)(, so it can make things appear larger than they are. A convex lens is curved like this(), making color go around and get put closer than they really are, making things appear smaller than they really are.