A man controls a robot at the fourth China Beijing International Fair for Trade in Services in Beijing, capital of China, May 30, 2016. Science and technology experience items attracted many visitors during the five-day fair that kicked off on May 28. (Xinhua/Zhang Chenlin)

A man looks at a police unmanned aerial vehicle at the fourth China Beijing International Fair for Trade in Services in Beijing, capital of China, May 30, 2016. Science and technology experience items attracted many visitors during the five-day fair that kicked off on May 28. (Xinhua/Zhang Chenlin)

Visitors experience brain wave vehicles at the fourth China Beijing International Fair for Trade in Services in Beijing, capital of China, May 30, 2016. Science and technology experience items attracted many visitors during the five-day fair that kicked off on May 28. (Xinhua/Zhang Chenlin)

A man experiences a driving simulator at the fourth China Beijing International Fair for Trade in Services in Beijing, capital of China, May 30, 2016. Science and technology experience items attracted many visitors during the five-day fair that kicked off on May 28. (Xinhua/Zhang Chenlin)

Photo taken on May 30, 2016 shows a LED plant cultivation equipment at the fourth China Beijing International Fair for Trade in Services in Beijing, capital of China. Science and technology experience items attracted many visitors during the five-day fair that kicked off on May 28. (Xinhua/Zhang Chenlin)