The Japanese yen dipped past the 160-per-dollar mark for a short time, making traders wonder if Japan might step in to steady its currency.
After a quick drop, thanks to rising US bond yields, the yen bounced back a bit and ended the day at 159.88 per dollar.
This move has everyone watching closely for what Japan might do next.
Traders cautious at 160, officials concerned
Traders like Juan Perez see 160 as a key level and are cautious about any big swings above it.
Japan's top currency official, Atsushi Mimura, said he's concerned about how fast the yen is moving, reminding folks of earlier interventions when things got out of hand.
Still, Howard Du, a strategist at TD Securities, thinks immediate action is unlikely but says everyone's keeping an eye out just in case things heat up again.