Dynamics　of　the　three　breakup　regimes　of　droplets　in　an　asymmetric　bifurcation　is　experimentally　studied　by　a　high-speed　microscope　system　and　a　micro-particle　image　velocimetry　(mu　PIV)　system.　Effects　of　the　droplet　length　and　the　capillary　number　on　the　evolution　of　the　neck　thickness　are　analyzed.　For　droplets　that　obstruct　the　microchannel,　the　pressure　drop　across　the　droplet　during　the　breakup　process　is　theoretically　calculated　and　its　relationship　with　the　neck　shrinkage　is　discussed.　Based　on　mass　conservation　law,　the　theoretical　prediction　on　the　geometric　shape　of　droplets　can　be　constructed　and　both　the　radius　of　droplet　rear　cap　and　the　neck　thickness　agree　well　with　experimental　results.　It　is　proven　that　the　theoretical　model　could　also　be　successfully　constructed　for　asymmetric　bifurcations　and　the　model　in　this　paper　could　be　applied　to　bifurcations　with　arbitrary　angles.　If　gaps　are　present　between　the　droplet　and　channel　sidewalls,　it　is　found　that　the　thinning　process　of　the　neck　and　variations　of　the　flow　field　of　droplets　are　distinctly　different　from　the　obstructed　breakup.　For　no　breakup　regime,　the　vortex　flow　accompanies　the　backflow　of　the　droplet　tip　and　two　different　vortex　distributions　within　the　droplet　are　disclosed　for　the　first　time,　which　are　separated　by　the　droplet　length.　The　critical　neck　thickness　that　determines　whether　droplets　break　after　flowing　through　the　bifurcation　is　revealed　and　compared　with　other　works.　(C)　2019　Elsevier　Ltd.　All　rights　reserved.