We present the results of HST WFPC2 observations of FS Tau and its environment obtained in the narrow-band emission line filters H \alpha and [ S II ] \lambda \lambda 6716 , 6731 \mathrm { { \AA } } .
Based on these data the morphology of line emission within this region can be studied on a size scale of 0 \farcs 1 for the first time . Despite the fact that FS Tau A has strong forbidden emission lines , there is no evidence for extended emission at these wavelengths beyond 0 \farcs 5 from the components of this close T Tauri binary system .
In the FS Tau B outflow interesting morphological properties can be studied at high spatial resolution .
In this jet we find a fine structure where circular or elliptical jet knots are correlated with mimima of the jet width .
The overall width of this jet decreases with distance from the source .
The FS Tau B jet is thus a rare example of a jet which may be recollimated far away from its source .
The jet is much more prominent in H \alpha than in [ S II ] , while the counterjet shows the opposite behaviour .
The line ratio H \alpha / [ S II ] increases with lateral distance from the jet axis , which is indicative of entrainment of ambient material .