It is (was) 被强调部分+that (who) + 句子其他部分。
此结构强调的成分仅限于主语，宾语和状语。强调句的连词只有两个，that和who。当强调的部分是人，且为句子的主语时，才用 "who"，其余用that。

原句： My father did the experiment in the lab yesterdayevening.
强调主语： Itwas my father who did the experiment in the lab yesterday evening.
强调宾语： Itwas the experiment that my father did in the lab yesterday evening.

强调时间： Itwas yesterday evening that my father did the experiment in the lab. (注意不用when)
强调地点： Itwas in the lab that my father did the experiment yesterday evening.