on to

preposition3

1. •
   Upon; on top of.

   • My cat just jumped on to the keyboard.
2. •
   (informal) Aware of.

   • The thought-police were on to my plans of world domination.
3. •
   Used to indicate, or signpost, logical progression to a new topic in a talk or discourse.

   • Now. On to the system of active water uptake.
   • Let's go on to item 3 in the list.