  Crystal seeding enables a deeper understanding of phase behavior, leading to
the development of methods for controlling and manipulating phase transitions
in various applications such as materials synthesis, crystallization processes,
and phase transformation engineering. How to seed a crystalline in time domain
is an open question, which is of great significant and may provide an avenue to
understand and control time-dependent quantum many-body physics. Here, we
utilize a microwave pulse as a seed to induce the formation of a discrete time
crystal in Floquet driven Rydberg atoms. In the experiment, the periodic
driving on Rydberg states acts as a seeded crystalline order in subspace, which
triggers the time-translation symmetry breaking across the entire ensemble. The
behavior of the emergent time crystal is elaborately linked to alterations in
the seed, such as the relative phase shift and the frequency difference, which
result in phase dependent seeding and corresponding shift in periodicity of the
time crystal, leading to embryonic synchronization. This result opens up new
possibilities for studying and harnessing time-dependent quantum many-body
phenomena, offering insights into the behavior of complex many-body systems
under seeding.
