Find an allusion related to exponential function.

The allusion related to exponential function is cell division.

Cell division is a very interesting phenomenon, and the speed at which new cells are produced is amazing. For example, a cell divides, 1 splits into two, two splits into four, and so on. Therefore, under ideal conditions, the functional relationship between the number of new cells y and the number of divisions x is: y = 2 (x).

General function y = a (x) (a is a constant, take a >；; 0, a≠ 1) is called exponential function, and the domain of the function is R. For all exponential functions, the range of values is (0, +∞).