Adaptive Edge Styles 

The gray edges in bar charts and histograms fade out as the width of the bars decreases to prevent the edges from overwhelming the actual bar styles.

In[1]:=

X Grid[Partition[Table[BarChart[Range@i], {i, {5, 25, 50, 100}}], 2]]

Out[1]=

In[2]:=

X Grid[Partition[ Table[Histogram[RandomVariate[NormalDistribution[0, 1], 200], i], {i, 10, 90, 10}], 3]]

Out[2]=