The TextSize property determines the pixel height of one line of rendered text. The unit is in screen pixels, not points (which is used in most document editing programs). The “Legacy” font does not hold this property.
This code sample repeatedly tweens a TextLabel’s TextSize from 5 to 100 and fades out the text as it grows in size.
local textLabel = script.Parent textLabel.Text = "Kaboom!" while true do for size = 5, 100, 5 do textLabel.TextSize = size textLabel.TextTransparency = size / 100 wait() end wait(1) end