 What we have done here is arrange the integers and the even integers into a "one-to-one correspondence" (or "bijection"), which is a function that maps between two sets such that each element of each set corresponds to a single element in the other set.However, not all infinite sets have the same cardinality.For example, Georg Cantor (who introduced this concept) demonstrated that the real numbers cannot be put into one-to-one correspondence with the natural numbers (non-negative integers), and therefore that the set of real numbers has a greater cardinality than the set of natural numbers.