The characteristics of turbulent/non-turbulent interfaces and turbulent/turbulent interfaces (TNTI and TTI) are analysed by new carefully designed direct numerical simulations (DNS). Whereas TNTIs separate the turbulent from the non-turbulent region in free shear flows and turbulent boundary layers, TTIs appear whenever two regions of distinct turbulent characteristics interact such as in turbulent jets and wakes surrounded by external turbulent flow, or strongly perturbed turbulent boundary layers, i.e., when the external flow is in turbulent condition. Direct numerical simulations (DNS) of temporally evolving and spatially evolving TTIs are carried out to analyse the conditional mean profiles of enstrophy. Preliminary results suggest that, if properly normalised using the mean local Kolmogorov velocity and length scale, these conditional mean profiles are universal.