Stem cell research is opening up new frontiers in medicine.

He is exploring the new frontier of science.

The time has come to start a new challenge.

He reclaimed the wasteland and turned it into farmland.

He was working hard to reclaim the wasteland.

He majors in medicine.

He is researching about a new energy source.

He is conducting research on a new energy source.

This trunk is very thick and strong.

There are many trees with large trunks in this park.