The slides the bioviewer takes is a specific type, often supplied with the device or available form bioviewer stockists.
The bioviewer takes no batteries and has no light source, it relies on ambient light which is focussed onto a white screen behind the slide in order to light the slide sufficiently. As such they are affordable, lightweight and fairly robust and maintenance free.
Sets of slides are available as 'Biosets' and cover topics such as:
Bioset slides are usually strips of eight related slide pictures accompanied by a text folder which explains what each slide is. Carry cases which can hold up to 10 bioviewers are also available for storage.