I know these are usually tutorials, but I encountered this very issue with my video editing and projects and I thought it would be pertinent to share it with you.
Final Cut Pro X updated, and with it went some apperance changes. In order to grow the clips in both the timeline and clip archives, you must now click a new button, or use the shortcut Command +. To shrink the clips, use Command -. This shortcut makes each second of footage take up either more space or less space.