Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Interstellar Grains -- The 75th Anniversary   The year of 2005 marks the 75th anniversary since Trumpler (1930) provided
the first definitive proof of interstellar grains by demonstrating the
existence of general absorption and reddening of starlight in the galactic
plane. This article reviews our progressive understanding of the nature of
interstellar dust.

18
The categories of this paper are: econ
30
The categories of this paper are: q-alg
12
The categories of this paper are: nucl-th
15
The categories of this paper are: nucl-ex
11
The categories of this paper are: hep-lat
31
The categories of this paper are: ao-sci
24
The categories of this paper are: dg-ga
27
The categories of this paper are: comp-gas
35
The categories of this paper are: mtrl-th
32
The categories of this paper are: atom-ph
10
The categories of this paper are: q-bio
23
The categories of this paper are: solv-int
22
The categories of this paper are: chao-dyn
21
The categories of this paper are: adap-org
26
The categories of this paper are: bayes-an
3
The categories of this paper are: physics