Each image in the 'film-strip' selector corresponds to a single Theiler Stage.
There isn't a 1:1 correspondence between Theiler Stage and age (days post conception or dpc). For each Theiler stage there will be an age range and an age corresponding to our model. If you 'mouse over' the film-strip images you will see the corresponding age range highlighted in magenta on the 'age scale-bar'.
By default Theiler stage 17 is selected (indicated by a green border round the film-strip image). To choose a different stage, either click on a different film-strip image or click on the up/down arrows in the stage selection box at the left-hand side of the selector. The age range corresponding to the the selected Theiler stage will be highlighted in green on the age scale-bar.
To move the film-strip, either use the left/right arrows (at the top left-hand side of the selector) or 'mouse down' and drag sideways in the film-strip.
You may prefer to specify an age rather than a Theiler stage and you can do this either by clicking on the age scale-bar or by clicking on the up/down arrows in the age selection box at the left-hand side of the selector. Your selected age will be indicated by a red 'cursor' on the age scale-bar.
If your selected age could correspond to more than one Theiler stage, the appropriate film-strip images will have a red border. You must now select a Theiler stage from the film-strip images with the red border.