After unlocking Blackbridge Grotto in Blue Prince you'll be introduced to a new kind of collectible item, the Microchip. These three collectibles, the first of which is obtained by simply accessing the Blackbridge Grotto, are used in a variety of puzzles including allowing you to obtain a special Blueprint.
First of all, if you haven't accessed Blackbridge Grotto yet be sure to do so with the help of our guide. To obtain the other two Microchips be sure to use our hints below.
Microchip #2 Location
Hint #1 - To find the hints for this microchip you must purchase 'A New Clue' from the Bookstore
Hint #2 - The Bookstore can only be drafted from the Library
Hint #3 - Take a closer look at the list of Corner Cases the detective is investigating
Hint #4 - Locate each of the rooms with checkmarks and review the notes in that room for anything that stands out
Hint #5 - Complete the instructions that you found

Microchip #3 Location
Hint #1 - To find the hints for this microchip you must purchase 'A New Clue' from the Bookstore
Hint #2 - The Bookstore can only be drafted from the Library
Hint #3 - Look for a visual clue in the record room that the detective is investigating in
Once you've put all three Microchips into the Blackbridge Grotto you'll get a cutscene and see the doorway open. Following this path up the mountain you'll be led to a table with the Throne Room Blueprint on it.