  Gravitational wave (GW) detection in space probes GW spectrum that is
inaccessible from the Earth. In addition to LISA project led by European Space
Agency, and the DECIGO detector proposed by the Japan Aerospace Exploration
Agency, two Chinese space-based GW observatories -- TianQin and Taiji -- are
planned to be launched in the 2030s. TianQin has a unique concept in its design
with a geocentric orbit. Taiji's design is similar to LISA, but is more
ambitious with longer arm distance. Both facilities are complementary to LISA,
considering that TianQin is sensitive to higher frequencies and Taiji probes
similar frequencies but with higher sensitivity. In this Perspective we explain
the concepts for both facilities and introduce the development milestones of
TianQin and Taiji projects in testing extraordinary technologies to pave the
way for future space-based GW detections. Considering that LISA, TianQin and
Taiji have similar scientific goals, all are scheduled to be launched around
the 2030s and will operate concurrently, we discuss possible collaborations
among them to improve GW source localization and characterization.
