Cells might have been disturbed or ran dry during pipetting steps. Please perform liquid removal and additions well-by-well. Avoid leaving neurons without any liquid coverage (medium or Nucleofector® Solution). To keep a small liquid film on the cells it is recommended to aspirate medium or solution individually from each well by using a pipette. Usage of a vacuum device is not recommended. Medium and solution removal and addition should be performed carefully at the edge of the well.