Wilhelm Wundt is usually viewed as the first psychologist to set up an experimental laboratory. By doing so, Wundt was trying to establish psychology as a legitimate science, separate from philosophy. He wanted to show that researchers could have well-controlled psychological experiments and systematically measure human behavior. With his work he did not seek to rule out non-experimental aspects of psychology, he just tried to establish that at least some aspects could be measured in a laboratory.
One key component of behavior that Wundt measured in his laboratory was reaction time, which he called mental chronometry. Wundt became interested in reaction time as a student of Helmholtz, who was the first to measure the speed of nerve reflexes. Wundt wanted to know how the brain related to basic nerve transit speed by testing reaction times. Wundt’s lab was able to incorporate the research of many scientists (including Donders’ subtractive method, which expanded on simple reaction times by establishing a reaction time baseline and then complicating the task by adding tasks) and use it to further our knowledge about psychophysiology.
Wundt’s greatest accomplishment was the establishment of his laboratory, which not only produced a lot of research but also trained a lot of future psychologist researchers, many of whom came from America. These trainees went on to other universities and established their own labs; some much like Wundt’s but with what they thought were improvements. Now, psychology labs are ubiquitous on university campuses. Much of Wundt’s writings have not been translated into English, so we (at least outside of German-speaking countries) do not know the entire significance of his work.