  The environments surrounding nine Wolf-Rayet stars were studied in molecular
emission. Expanding shells were detected surrounding these WR stars (see left
panels of Figure 1). The average masses and radii of the molecular cores
surrounding these WR stars anti-correlate with the WR stellar wind velocities
(middle panels of Figure 1), indicating the WR stars has great impact on their
environments. The number density of Young Stellar Objects (YSOs) is enhanced in
the molecular shells at $\sim$5 arcmin from the central WR star (lower-right
panel of Figure 1). Through detailed studies of the molecular shells and YSOs,
we find strong evidences of triggered star formation in the fragmented
molecular shells (\cite[Liu et al. 2010]{liu_etal12}
