Related Clues:

• Like nuclear energy
• Teeny, informally
• __-bitsy (tiny)
• Of interest to some physicists
• __ bit
• Minuscule, informally
• Kind of clock or bomb
• Giant's antithesis
• Opposite of 55-Down, informally
• Quite tiny
• Bitty start?
• The ___ early hours
• Early, as hours
• Word for Willie Winkie
• Short period of time