Fibonacci Sum of Squares

One can easily see that the length and breadth of the above rectangle are $\mathcal{F_{n+1}}$and $\mathcal{F_{n}}$.

Area of the rectangle = $\sum$ Area of the squares
or,$$\mathcal{F_{n}F_{n+1}=F_{0}^{2}+F_{1}^{2}+\cdots+F_{n}^{2}}$$