An essential matrix relates corresponding points between two images assuming that a camera satisfies the pinhole camera model, and can be expressed as: $$E=K'^TFK$$
where K is the calibration and F is the fundamental matrix.
There are many tools to compute the essential matrix, one of them using OpenCV's function findEssentialMat. You are typically returned a 3x3 matrix which contains the transformation (or the $$E=R[t]_x$$ camera pose version). Typically, the translation is directly extracted from the t part, and the rotation matrix has more than one solution.
However, how is scaling represented in the essential matrix?
In case it is, how can one extract it? In case it isn't, how come it isn't> And how should one include it to properly state the total motion between the images' points?