Find the cell on the path is a mission in The Precursor Legacy that Jak and Daxter complete to earn a power cell. Taking place at Geyser Rock, it is the very first mission of the game. Although it is part of the training course required by Samos Hagai, it is technically assigned by Keira after she briefly explains the purpose of a power cell via communicator.
Walkthrough[]
After exiting the warp gate, use the left analog stick (
) to approach a group of Precursor orbs. Use 
to jump onto the tiered ledges and collect a couple orbs, soon after which Keira will interrupt to explain their purpose.
Next, move forward to approach a trio of orbs floating across a spike-filled gap. Keira will interrupt to explain the power cell that sits on the other side, surrounded by some test dummies. Keira explains that the power cell is the "most important Precursor artifact you can find", and that Jak will need to "collect twenty of these so that I can power the heat shield for your A-Grav Zoomer."[1]
After this, either jump across the gap or move around it using the cliffs on either side, then simply walk into the power cell to collect the first of the game.