If properly managed, clearing and replanting trees in a 30-year cycle creates both a renewable source of energy and maximum rubber production.

VOA: standard.2009.09.13

So we needed to come up with another source, a renewable source, so we turned our attention to embryonic stem cells.

因此，我们需要一种替代材料，一种可以再生的材料，我们注意到了胚胎干细胞胚胎干细胞。

斯坦福公开课 - 7个颠覆你思想的演讲课程节选