Facial expressions stand out as one of the most powerful non-verbal ways to express human emotions and intentions. These expressions are often deliberate and socially regulated, making them more straightforward to analyze and understand. In addition to these ordinary facial expressions, known as macro-expressions, that we observe daily, there are also spontaneous facial expressions, especially micro-expressions, are involuntary, subtle and occur briefly, often without the awareness of the individual displaying them. These unique characteristics make micro-expressions challenge to detect. To better understand the rapid and involuntary nature of micro-expression, we utilize the optical flow algorithm to calculate facial movements between the onset and apex frame of the micro-expression videos.