Exocytosis is a process that involves<span> proteins in vesicles being held at the plasma membrane until the cell is signaled to release them. The product of this process will be packaged into the transport vehicles and then fuse them with the plasma membrane.</span><span> </span>
When the electron wavefunction is bound in a stable state in an atom it stretches into a 'orbital' form. There was a mistake. When attached in a stable atomic state, an electron often acts like a three-dimensional oscillating wave, i.e. the orbital vibrates. It's sort of like a vibrating chord.
Stem cells are what allow planaria to grow and regenerate as the stem cells can change into any of the cells that make up the planaria.