The following pictures show n unit squares packed inside the smallest known domino (of shortest side length s).
1-2. 
s = 1
Trivial.
3. 
s = 3/2 = 1.5
Trivial.
4. 
s = 1.930+
Found by Evert Stenlund
in June 2010.
5-8. 
s = 2
Trivial.
9. 
s = 2 + √2/3 = 2.471+
Found by Evert Stenlund
in June 2010.
10. 
s = 5/2 = 2.5
Trivial.
11. 
s = 2.779+
Found by Evert Stenlund
in June 2010.
12. 
s = 6 (1 + √2) / 5 = 2.897+
Found by Maurizio Morandi
in June 2010.
13. 
s = 2.976+
Found by David W. Cantrell
in July 2012 (after Maurizio
Morandi in June 2010.)
14-18. 
s = 3
Trivial.
19. 
s = 3 + 1/√5 = 3.447+
Found by Maurizio Morandi
in June 2010.
20-21. 
s = 7/2 = 3.5
Trivial.
22. 
s = 3.745+
Found by David W. Cantrell
in July 2012 (after Maurizio
Morandi in June 2010.)
23. 
s = 3.849+
Found by Maurizio Morandi
in June 2010.
24. 
s = 3.882+
Found by DC after MM
in August 2012.
25. 
s = 3.939+
Found by DC after MM
in August 2012.
26. 
s = 3.981+
Found by David W. Cantrell
in July 2012 (after Maurizio
Morandi in July 2012.)
27-32. 
s = 4
Trivial.
33. 
s = 3 + √2 = 4.414+
Found by Maurizio Morandi
in July 2012.
34. 
s = 4 + √2/3 = 4.471+
Found by David W. Cantrell
in July 2012.
35-36. 
s = 9/2 = 4.5
Trivial.
37. 
s = 10 / 3 + √2 = 4.747+
Found by Maurizio Morandi
in August 2012.
38. 
s = (13 + √2) / 3 = 4.804+
Found by Maurizio Morandi
in August 2012.
39. 
s = 4.839+
Found by David W. Cantrell
in August 2012.
40. 
s = 4.895+
Found by Sigvart Brendberg
in June 2023.
41. 
s = 4.927+
Found by Sigvart Brendberg
in June 2023.
42. 
s = 4.989+
Found by David W. Cantrell
in August 2012.
43-50. 
s = 5
Trivial.