The most interesting place in a tropical forest remains a virtually unexplored domain. The treetops, where many plants and animals - including many little-known species - spend their entire lives, have been out of scientists' reach.

For years, tropical biologists got their only glimpse of the forest canopy when a tree crashed to the ground. And a few athletic scientists managed to ascend into a biological heaven with ropes and pulleys, but the work was cumbersome and dangerous.Now biologists have devised a way to gain almost unlimited access to the canopy. They have installed a construction crane in the forest.

The technique is being tested by scientists with the Smithsonian Tropical Research Institute, who erected the crane in a forested park near Panama City. A researcher sits in a gondola, which swings out along the length of the crane. The biologist can then lower the gondola into the treetops.

"It's wonderful," said the Smithsonian's Alan Smith. "There is more biology in that 80-meter radius than a team of biologists could cover in a lifetime."