over and underbrace brace in Tex

Use the Tex code below to generated upper and lower brace

\overbrace{your-formula}^\text{your comment} 
\underbrace{your-formula}_\text{your comment} 

The code below will give this result $$ s = \overbrace{ \underbrace{\sigma}_\text{real} + \underbrace{j\omega}_\text{imaginary} }^\text{complex number}$$

\[
  z = \overbrace{
    \underbrace{x}_\text{real} +
    \underbrace{iy}_\text{imaginary}
   }^\text{complex number}
 \]