SPY555-FastActâ„¢ is a bright, orange, fluorogenic & non toxic F-actin stain based on SPYâ„¢ dyes series. Its optimized structure allows to label F-actin in live cells with high specificity and low background. The unique and unmatched feature of SPY555-FastActâ„¢ is its ability to label very dynamic actin, like LifeActâ„¢* but the probe does not require any genetic manipulation, transfection or overexpression of fluorescent proteins. SPY555-FastActâ„¢ is based on our bright, photostable & orange SPY555 fluorophore which is far superior than fluorescent proteins. SPY555-FastActâ„¢ enables multicolor imaging with SPY505, SPY595, SPY650, SPY700, SiR and GFP. SPY555-FastActâ„¢ can be imaged with standard TMR or Cy3 settings. It can be used for widefield, confocal, SIM or STED imaging of living cells and tissue. *LifeActâ„¢ is a registered trademark of Ibidi GmbH.