Complex sentence: In 1794, he began his scientific studies at the Collège Calvin, where he studied under Jean Pierre Étienne Vaucher, who first inspired Candolle to make botanical science the chief pursuit of his life.
Split into simpler sentences: In 1794, he began his scientific studies at the Collège Calvin, where he studied under Jean Pierre Étienne Vaucher. It was Vaucher who first inspired de Candolle to make botanical science the chief pursuit of his life.