In the second aliyah of Parshas Toldos, we learn about Yitzchak's encounter with Avimelech. This is the only time where laughter is mentioned in connection to Yitzchak, other than when he was named. There are two different kinds of laughter-the laughter of unrestrained joy, and an internal laugh, like that of Sarah Imeinu. Yitzchak's laughter is the restrained, internal kind, reflected in his middah of gevurah. This restraint is expressed in the limitations of nature, but Yitzchak teaches us that even with the hiddenness we can find and connect to Hashem.